John C. Taylor

John Fromanteel's

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It has been widely accepted that, after Huygens adapted a table clock to be controlled by a pendulum and transferred his patent rights to his design to Salomon Coster, Ahasuerus Fromanteel in London heard of these new pendulum clock developments and arranged to send his son, John, who had just finished his apprenticeship, to The Hague to learn this new construction at firsthand. A contract was drawn up in The Hague to set the terms of John’s wages and this technology transfer from Holland to England.

In this article I set out to show that the actual wording within the contract itself does not support the above synopsis. Rather I submit that the contract was drawn up under the premise that John travelled to Holland ready to start work, knowing the layout of the clock trains he contracted to make. I submit that John brought to Coster’s workshop all his own brass castings and the necessary steel with him to work for nine months. The contract was necessary to ensure that John was paid not only for his labour and his brass and steel but also high enough fees to cover the design and development costs of the clock in London. It also ensured that Salomon was forced to purchase all John’s production of clocks from these kits of parts he brought with him. If John used up his own brass and steel, only then would Salomon supply him with further raw materials and John’s fee would be reduced.


There are five extant early domestic pendulum timepieces signed by Salomon Coster; Dr Reinier Plomp points out their similarity and agrees with L.H.J. van Lieshout’s suggestion that all these movements were made under contract by John Fromanteel for Coster (1. They all have similar sized plates, square pillars (2 and a delicate, pleasing train of brass wheels driving steel (3 pinions.

Five early pendulum clocks

The contract between John Fromanteel and Salomon Coster has been subjected to much detailed analysis over the years. One aspect of the contract that appears to have excited little scrutiny by any reviewer, is the monetary consideration to be paid by Salomon to John for the clock movements that he produced. In the translation by Frits van Kersen the signed contract reads:

... for each piece [clock movement] being of brass and steel, therefore he Coster will pay him a sum of twenty car. guild.

This clause assumes that John will most likely supply his own brass and steel and receive twenty guilders. This conclusion is further strengthened by the exception that now follows:

And if the aforementioned brass and steel will be delivered by aforementioned Salomon Coster himself, [ie if all the brass and steel are supplied by Coster] then he Fromanteel therefore will enjoy no more as 18-10-0,(4


Coster clocks
Price list in guilders, Jan. 1659
Weight Spring Striking 30 hr. 8 day Price

In a letter by Huygens to Boulliau dated 16 January 1659 we find a specification of the various clocks deliverable by Coster, including prices.

Dr Reinier Plomp gives ‘the price of a complete Coster timepiece going 30 hours, listed by Huygens as D.fl 80 ...’.(5 This is the retail price; Huygens’ letters do not contain information on Coster’s ex-works price.(6 This is not the place to discuss Business School type market theories such as ‘Demand for a product increases at least tenfold if the price is halved’, but this retail price of eighty guilders, set for the world’s first accurate to a minute domestic pendulum timepiece, has to achieve two interlinked but different competing objectives:

   1. The price has to be low enough to entice buyers. If the price is set too high there may be no buyers to come forward to purchase these new but unproven clocks. People in general do not like to be the first to buy an innovative but untried product.

   2. The price has to be high enough to restrict sales. If the price is set too low, Huygens would have been overwhelmed with orders that Salomon would be unable to fulfil. If goods are not delivered promptly customers quickly become disillusioned and cancel their orders; they fear the possibility of a swindle: the product is then condemned by word of mouth making further sales virtually impossible. An insatiable demand from too low a price would result in a huge loss of face for Huygens. A further Business School theory is: ‘It is always possible to reduce price but it is difficult or impossible to increase it without killing all the product’s pent up demand.’ It would appear that Huygens did set his retail price high enough to ensure he was not overwhelmed with orders that Salomon was unable to fulfil; thus his eighty golden guilders was therefore a high price.


The modern perceived wisdom of the seventeenth century is that labour was cheap and materials were expensive. However, John’s labour costing 18½ guilders and the materials in the movement costing only 1½ guilders, appears to turn this generalisation on its head to expensive labour(7 and cheap materials.
   After paying John his direct cost for his materials and labour, Salomon’s ex-works price still had also to cover the costs of the dial, velvet, silver or silvered chapter ring and lambrequin, hour and minute hands, wooden case with its door, glass and lock with the key, two pairs of hinges and hanging eyes and all the materials and labour. More direct costs were involved in final assembly, setting up the pendulum, bringing to time and testing. Each clock then had to be partly disassembled, carefully packed most probably into a custom-made transit wooden box before the whole was wrapped in protective padding such as being sown into a hessian sack; then there are all the costs of delivery. In addition, Salomon’s overheads included his own wages, rent and taxes on his workshop, repairs and maintenance, heating, lighting, legal fees, interest and finance costs, postage and a host of other small business costs.
   Huygens then had to unpack and check the clocks for delivery damage, repack, deliver and set up the clock for his customer as well as finance the whole transaction. He had his patent fees, travel costs and advertising correspondence. He had Horologium for the scientific kudos and, although his correspondence may remain silent, I find it difficult to believe that he went to the trouble and expense of patent applications together with the delivery costs if this broughthim no personal pecuniary advantage.
   Thus John’s labour appears a very high percentage of the final retail price in comparison with Salomon and Christiaan’s large additional costs and overheads.
   In the translation ‘And yet with that condition: if the aforementioned brass and steel…’ the original Dutch ‘indien’ may be more literally translated into ‘in case’ further changing the emphasis slightly ‘And yet with that condition: in case the aforementioned brass and steel...’. The contract uses ‘if ’ or ‘in case’ to imply an unlikely event rather than stating ‘when’ to imply a likely event that Salomon has to supply (all) the brass and steel to John whereby John receives only 18½ car. gld.

Fig. 1
Side view of a John Fromanteel movement in a Coster timepiece dated 1658, showing the movement. Note the square pillars, typical for Fromanteel’s early style.

Thus it is logical to assume John was to start off supplying all his own brass and steel and Salomon would take over the supply if and only if John had used up all his own brass and steel.


We can draw four conclusions from this clause on the fee in the contract:

   1. It assumes that John will most likely supply all his own brass and steel and receive twenty guilders for a completed movement.

   2. This is an all or nothing requirement, no consideration is postulated in the agreement if John has to obtain even one small piece of brass or steel from Salomon. Thus neither of the signatories to the contract considered this a likelihood.

   3. In the unlikely event that Salomon has to supply John with all the necessary brass and steel for a complete movement, John will only receive 18½ guilders.

   4. John’s labour was particularly costly at 23 per cent of the 80 guilders retail selling price of the finished clock.


The above conclusions raise further questions that are the crux of this article:

   1. Why should John’s labour appear so expensive?

   2. How did John Fromanteel know what brass and steel were necessary for the clock movements he was contracting to make?

   3. From where did he obtain his brass and steel that the contract assumes that he will use? There is no mention in the contract of wood for the clock cases, velvet dial covering, nor of silvered parts and engraving and it is generally accepted that ‘each piece’ in the contract refers solely to the clock movements. Salomon was to supply the rest of the visual components, dial, etc. and the complete case.

Some of the Coster signed clocks have brass dial plates and some have steel dial plates.(8


The five extant movements supplied by John under the contract are all very similar with matching sets of brass component listed in Table 1.

All twenty-nine brass parts were made from twenty-five different types of castings, each requiring their own patterns.(9 The raw castings had to be hammered to toughen up the soft brass and then worked and filed up into precision parts for the clock. For example, the flat spring barrel casting would be hammered round, the ends brazed together and then turned on a pole lathe to perfect size. Wheel cutting engines, I understand, were not yet perfected and wheels and pinions were marked out and sawn and filed to shape. This was the work that John was undertaking together with forging, turning and filing the main steel parts. These would most likely have been made from steel bar or rod and have been as listed in Table 2.

End of this section, click here to continue.


1 Reinier Plomp, ‘The Prototypes of ‘Hague Clocks and ‘Pendules Religieuses’ ’, Antiquarian Horology 30/2 (June 2007), 196-208, esp. pages 198-9 (listing the five known timepieces), 201 and Conclusion 2 on p. 208. 
2 Square pillars are a feature of the earliest extant English pendulum clocks signed by Ahasuerus Fromanteel, see exhibits 7 and 8 in the catalogue of the 2003 AHS exhibition Horological Masterworks.
3 I make no differentiation between ‘steel’ as quoted in the translation of the contract and ‘iron’ as often referred to by Dr Plomp in his articles, as I feel both words are intended to describe the ferrous material in common use at the time. I simply use ‘steel’ throughout for consistency.
4 Frits van Kersen, ‘The Coster-Fromanteel Contract Re-examined’, Antiquarian Horology 28/5 (March 2005), 561-67. I am grateful for Frits van Kersen for helping with the nuances of the Dutch language together with the chronology and help in correcting my dyslexic orthography. All mistakes remaining are entirely my own.
5 Plomp, ‘The Prototypes’, p. 201. D.fl = Dutch florin is interchangeable with a Carolus guilder.
6  H.M. Vehmeyer, Clocks, Their Origin and Development 1320-1880 (2005), p. 227: ‘Coster’s function seems to have been limited to the contacts with Huygens and the actual production’.
7 Vehmeyer, Clocks, p. 225: ‘the average worker earned at best 40 guilders in a whole year’.  
8 Plomp, ‘The Prototypes’, p. 200.
9 At the AHS reception on 26 February 2008 at the Oxford Museum for the History of Science for the display of the newly restored Ahasuerus Fromanteel roller cage longcase of c. 1661, the restorer Matthew Read made the point that all the brass wheels were cast with the crossings in place. Under close examination he could still observe the finishing to clean up the casting surfaces on the crossings.
10 G.F.C. Gordon, Clockmaking Past and Present (1946), Materials p. 5, Motive Power p. 65. See also Vehmeyer, Clocks,
p. 225: ‘Generally speaking, the latter type [spring driven] are more expensive’ [than weight driven].
11 Percy G. Dawson, C.B. Drover and D.W. Parkes, Early English Clocks (Antique Collectors’ Club, 1999), p. 7.
12 J.H. Leopold, ‘Some more thoughts on the Coster-Fromanteel Contract’, Antiquarian Horology 28/5 (March 2005), 568-70 (p. 568).
13 Van Kersen, ‘The Coster-Fromanteel Contract Re-examined’, p. 563.
14 Rebecca Pohancenik, ‘The Intelligencer and the Instrument Maker: Early Communications in the Development of the Pendulum Clock’, Antiquarian Horology 31/6 (December 2009), 747-56; esp. pages 747 and 752.
15  Huygens’ Legacy: The Golden Age of the Pendulum Clock at the Royal Palace Het Loo, 2004, exhibits 5 and 6 in the catalogue.
16 I am indebted to Michael Hurst for this information.
17 Plomp, ‘The Prototypes’, p. 208.
18 Plomp, ‘The Prototypes’, p. 196.
19 Huygens’ Legacy, exhibit 8
20 E.L. Edwards and R.D. Dobson, ‘The Fromanteels and the Pendulum Clock’, Antiquarian Horology 14/3 (September 1983), 250-165 (p. 253).

back to early pendulum clocks  

Table of contents:

The five early Coster clocks
Perceived wisdom of the 17th C.
Four conclusions
The Crux
Matching sets of brass components
The expensive mainspring
To supply or not to supply
English pendulum clocks before the contract
Drawings and Specifications
Deduction from the contract
About the author

This article was first published in the Sept. 2010
issue of Antiquarian Horology.


Technically the most difficult steel part is the clock main spring. Each clock design requires a unique motive driving energy store, matched to the duration, the particular train and the chosen pendulum. The spring in the Coster timepieces is particularly difficult as no fusee is used to even out the decay in the spring action as it unwound.
G.F.C. Gordon writes at length on the problems that the early metal workers had in making thin steel springs and how only the most costly movements were spring driven.
He writes ‘…for one satisfactory bracket clock spring which was made and used, ten or even fifty were tried and rejected.’(10 This large, easily seen, spring driven domestic timepiece, accurate to show meaningful minutes for the first time ever, was the pinnacle of scientific achievement and technological manufacturing: in modern terms, high technology, coveted consumer designer product; the expensive ‘must have boys toy’ from the middle of the seventeenth century. Huygens reports in his diary that he had the pleasure of adapting his first model pendulum clock on Christmas Day 1656 and by June 1657 a patent had been granted to Salomon Coster.(11

TABLE 1 Casting patterns Brass parts

Front plate and back plate 1 1
Square movement pillars 1 4
Great wheel, spring barrel and barrel cap 3 3
Click wheel and click spring 2 2
First wheel 1 1
Contrate wheel 1 1
Escape wheel 1 1
Cannon wheel 1 1
Minute wheel 1 1
Hour wheel and integral pipe 2 2
Crutch and crutch block 2 2
Pendulum bob and rating nut 2 2
Top pottence and bottom potence 2 2
Backcock, left and right cheeks 3 3
Motion work bridge 1 1
Clock winding key 1 1

Totals 25 29

TABLE 2 Steel parts

First arbor and pinion 1
Contrate arbor and pinion 1
Escape wheel arbor and pinion 1
Minute wheel pinion 1
Verge arbor and pallets 1
Hook for main spring in brass barrel 1
Winding click 1
Crown wheel lower bearing 1
Tapered pendulum rod 1
Miscellaneous screws 8
Miscellaneous taper pins 4
Clock spring - the most expensive component in the clock 1

Totals 23

Therefore one might probably assume that casting patterns and raw castings from a Dutch brass foundry must have been available
in Coster’s workshop when John Fromanteel arrived in The Hague in late summer 1657.


For any subcontractor, it is financially disadvantageous to supply your own materials. Apart from your own personal cash tied up in the stock, you personally stand the loss if parts are lost or damaged or the dimensions are changed and the components are scrapped. Any faults or mistakes needing replacement are your
own materials and your personal costs. Thus it is normal practice and to the advantage of subcontract craftsmen to solely sell their labour leaving their employer to supply all the materials on which they perform their work.
If John supplied his own brass and steel, any faulty finishing work requiring a new raw piece was his own personal financial loss: it was not in John’s interest to supply his own materials, particularly if there was any development still taking place that might make any parts obsolete. It was to John’s benefit to have Salomon supply all the brass and steel for him to work up and finish to a going clock movement. Yet the contract specifically implies that the most likely scenario is that John, a 19 year old newly arrived in a foreign land, will take the responsibility to supply all his own brass and steel! How and why would he do this?
Even with John’s likely command of the language,(12 if, as suggested,(13 he had worked for a week or two in Salomon’s workshop, using Salomon’s brass and steel:

   1. It seems inconceivable that John decided that Salomon’s brass and steel were of inadequate quality, or of such a high price from the Dutch suppliers that he could make a profit from supplying his own parts.

   2. It appears unlikely that he could visit Salomon’s local Dutch suppliers and negotiate a better price than Salomon to make it worth his while financially to take on the responsibility of supplying all his own brass and steel.

   3. If the castings were not yet available, it would be unlikely for John as a young itinerant craftsman to have the cash with him to pay for the patterns to be produced and finance the necessary batches of brass castings and necessary steel, particularly as he only was paid for the materials he used after he had completed each movement.

   4. Equally implausible is the thought that he had to draw up each and every part and either send the drawings or took the drawings or a set of parts back to London to enable a quotation to be prepared and then sets of parts produced and shipped over prior to the contract being signed.

   5. Nevertheless, he went with Salomon before a Notary and signed a contract thereby taking the full responsibility to normally supply all his own brass and steel.


Rebecca Pohancenik has recently established that Ahasuerus Fromanteel had indeed manufactured and sold pendulum clocks prior to John Fromanteel’s sojourn with Salomon Coster. She also links Christiaan Huygens with Ahasuerus Fromanteel, giving further insight into the origin of possible technical collaboration.(14

The little table clocks by Coster exhibited at Het Loo(15 have beautifully shaped pillars. Square pillars were not a natural progression for Coster. With no power lathes available to turn up round and complex shaped pillars, such attractive shapes took much care and effort to produce on a bow lathe. All the extant very early pendulum clocks signed by Ahasuerus Fromanteel have square pillars. These appear to be unique to Ahasuerus’ signed early pendulum clocks. Square brass pillars can be produced from a raw casting, not just by filing but by hammering the brass to a tough regular shape,(16 leaving just the two ends to be turned round on a lathe. Moreover, Ahasuerus was an experienced blacksmith and used to hammering metal into shape. Coster was under pressure to produce sufficient clocks to meet Huygens’ demand and accepted the Fromanteel quicker if less visually attractive option.

It is not necessary for me to postulate that the springs, brass castings, etc were actually made in the Fromanteel workshop; they may have been made by specialists nearby in London; I solely suggest that John must have brought these components with him to The Hague if he was to sign a contract to supply them.

I conclude that John Fromanteel arrived at Salomon Coster’s workshop and signed the contract knowing what brass and steel was required and brought with him several complete sets of brass castings, together with the necessary steel rod and bar, as well as the necessary clock springs. Only if all these conditions were met would the contract have been drawn up as it was.

It was John who needed a contract and had it altered to ensure he had:

   1. A fixed price for the work and materials he supplied.

   2. A guaranteed market for the movements he produced.

   3. A high price to cover any development work that had already taken place in London and perfections still to take place in The Hague.

Almost the last clause in the contract gives
John this necessary assurance:

... provided the works by which he Fromanteel on the conditions aforementioned will have been made, he Coster for the stipulated price will be allowed and obliged to keep.

In other words if John makes the movements, he is going to sell them to Salomon and Salomon is required to pay 20 guilders for them.
Plomp in his conclusion no. 2 says:

The movements of the five Coster timepieces are so similar that it is justified to conclude that they represent the movements referred to in the contract between Salomon Coster and John Fromanteel.(17

To this I would add: ‘and made from a kit of brass and steel parts and the main springs brought with him from London’.


We may now conclude that there were at the very least letters, drawings and specifications of the movements passed between Coster and the Fromanteels before John’s visit in September 1657. Most likely one or more sample movements were produced in London before the approval for the production of the unique brass castings and mainsprings for John to take with him to The Hague.
This also opens for further discussion the clauses in the contract and a literal interpretation of the following two phrases:

   1. ‘John Fromanteel obliges and commits himself to execute and perfect his watchwork
…’ as an indication that the Coster/Fromanteel design was still not finalised and some perfection of the mechanism was still to be undertaken by John. The earliest signed Coster pendulum clock dated 1657 was found in 1922 by Drummond Robertson in the Rijksmuseum (as he reports: subsequently lost) together with the present earliest extant clock also dated 1657.(18 Whilst the trains were very similar the first clock solely had an hour hand whereas the later clock also has a minute hand.(19 Was this the perfection to be carried out by John?

   2.‘…like he Fromanteel already has made some’ was as a further substantiation that John had already been producing prototype Coster pendulum clocks in London. This phrase in the contract was considered by either Salomon or John or both as an important additional clause added into the contract as it is inserted, crossed out and inserted again in a different place to strengthen the point.

E.L. Edwards and R.D. Dobson note that the backplate of the earlier Rijksmuseum clock was signed ‘Samuel Coster Haghe met privilege’ and point out that signing on the backplate is an English, not a Dutch tradition. As Salomon corrects a similar mistake over his name in a contemporary document, they surmise that this clock must have been made by John without Salomon’s input,(20 to which I would add: ‘in London prior to his visit to The Hague’.


I conclude that the Fromanteel family expertise facilitated in preparing the Fromanteel/Coster design in London so that the necessary kits of brass castings and steel together with the mainsprings could be produced for John to take to The Hague with him, ready to start work. But it was necessity for John to have a contract to ensure he was paid a suitable high fee as this was also to cover the Fromanteel development work in London and not just his own labour costs. This can all be deduced from the contract.

About the author

Dr John C. Taylor is an inventor with about two hundred British patents in his name. The company he founded in 1981 won four Queen’s Awards and last year celebrated selling one billion kettle controls. His interest in horology started through navigation – trying to fly a small aircraft from Manchester to Tokyo. His latest invention is the Corpus Chronophage. (


The Horological Foundation is endebted to the Antiquarian Horological Society for making their PDF version of the original printed article available.

Photo 1: Courtesy of Dr. John C. Taylor, Isle of Man

May 2019, Copyright: John C. Taylor


Chr. Huygens' Œuvres Complètes. (pdf)

Chr. Huygens Horologium 1658. (pdf)

The Coster Fromanteel Contract. The Van der Horst transcription working sheet. (also PDF)


(This article is subject to ongoing revisions.)

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