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As soon as the news of the development of an electro-mechanical movement by ‘LIP’ and ‘Elgin’ hit the Swiss watch industry in 1952 and the announcement of the patent for a battery driven watch using a tuning fork as timing device in 1954, efforts were made to counteract this revolutionary steps coming from the French / American collaboration of ‘LIP’ and ‘Elgin’ and the American ‘Bulova’ company.
Whereas most Swiss watch manufacturers decided to ignore what seemed to be exotic and short lived systems, other manufacturers such as Omega and Ebauches SA started to pursue their own paths towards an electric watch.
The first successful Swiss attempt was the electro-mechanical movement L4750. The first working prototypes for the L4750 movement were made in 1954/55. These first prototypes had already either a rechargeable battery integrated into the case back or two batteries (one would be a replacement battery) located at the top part of the strap. Once the movement was finalised in 1960, both battery alimentation versions were marketed.
Despite their short production period these movements have been used by over 80 brands or retailers. Also, there are two versions of both movements with 12 or 13 jewels respectively, latter version can also be found with a chronometer certification (1).
Specific maintenance and regulation devices have been developed to ensure proper functionality (1).
ESA L4750 Prototype / Sample, 1960 ; ESA L4751 Prototype / Sample, 1961
Category: aesthetic prototypes / samples
Description: Symmetric, gilt, base metal cased prototypes with polished surfaces (EPSA, E. Piquerez SA). Two part stainless steel case back with screwed battery hatch. Back engraved ‘Ebauches SA Electric 4750 – Choc Absorber – Waterproof’. The engraving being identical on both watches. Battery hatch of L4750 prototype engraved with ‘1236.3’. Silver, polished (L4750) and linen decorated (L4751) dials. Gilt 15min, raised indexes, black printed minute indexes (L4750), gold coloured 5 min indexes (L4751). ‘ESA’ logo and ‘Electric’ in black at ’12’, ‘4750’ and ‘4751’ respectively above ‘6’, ‘Swiss Made’ below ‘6’. Lume dots at 15min marks (L4751). Fancy gilt hands, ‘lightning’ decorated seconds hand (L4750). Gilt, baton hands with lume (L4751). Acrylic crystal, Gilt, base metal crown with cross hatching decoration on both.
Dimensions (both): 35mm (without crown), lug – lug: 44mm, lug width: 19mm
Movements: Left: L(anderon) 4750 ; Right: L(anderon) 4751, #6687
Additional info: Both systems were rather short lived, the later version L4751 was only produced for 6 months. This illustrates the speed at which the development of electric watches was advancing during the early 1960s. Both systems are virtually identical, with slight construction differences and the later L4751 having the addition of the second-stop lever when the crown is pulled to allow for precise synchronisation. Moreover, the declared battery life for calibre L4751 is of 24 months, whereas the battery life of calibre L4750 would be of 8 – 12 months. Both versions, L4750 and L4751, came in two versions: normal battery or rechargeable battery. The versions with normal battery show the battery life mentioned before, the one with rechargeable battery have a declared battery life of 6 months (1).
The overall size of the movements is practically the same, L4751 being 0.65mm thicker than its predecessor (1).
These watch types can also be found in the form of school watches, where the goal was to introduce the system of electric watches during the apprenticeship phase in watchmaker schools. Most school watches of this type are cased in stainless steel, are signed with the school name on the dial and feature an almost invisible engraving of the student number on the case back. The version shown here has a press in case back which is engraved with the production info of the marketed versions.
Some examples of such school watches are repurposed samples or aesthetic prototypes which were sponsored by the watch or movement manufacturers for use in watchmaking schools.
More information about the development of these movements, electro – mechanical movements in general and the ‘Swiss quartz evolution’ can be found in the parent section.
Ref.:
Electric Watch Prototypes 