Stainless-steel cased automatic winding centre-seconds club-tooth lever wrist-watch with date mechanism and blue leather strap

Description — British Museum

Wrist-watch. Movement with automatic winding and fast beating train (10 beats per second); club-tooth lever escapement. Black painted dial with outer adjustable seconds ring, orange coloured and numbered every fifth division in Arabic; baton hour marks with luminous bands; sector aperture between 4 and 5 reveals date indication. Steel hour hand and orange coloured minute hand; white painted centre-seconds hand. Stainless steel case with screw-on bezel and back. Blue leather wrist-strap.

Curator's comments — British Museum

In around 1970 it seems Longines changed from numbering their movements moving to numbers starting 50#######, suggesting that this watch dates to not long after the change. Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript) Made by LONGINES WATCH Co. Switzerland, c. 1967 A self winding calendar wrist watch with a club tooth lever escapement and a fast beat rate. Signature: On the dial 'LONGINES' with their trade mark, 'automatic' and 'ULTRACHRON' also - 'T SWISS MADE T' -. On the self winding weight 'LONGINES'. On the train bridge 'LONGINES WATCH Co SWISS SEVENTEEN 17 JEWELS'. In a rectangle 431 and 50080793. Case: A tonneau shaped case of stainless steel. The screw back is marked inside 'LONGINES' with the trade mark below 'FAB SUISSE MADE ACIER INOXYDABLE 8221-2 431 SUPER COMPRESSOR BREVET + 317537 BREVET + 337462 DDE BREVET + 7633/66 11685/66 4678/67 4 69'. The threaded portion of this back is a separate piece held in place by a stout crinkle spring. Movement of the ring relative to the back in a circumferential way is prevented by lugs that penetrate four gaps in the screw ring flange. The object of this is to secure perfect alignment of the flange on the back where it meets the mating surface of the case, the part that carries the rubber sealing ring. The case is additionally fitted with a separate and moveable minute ring. This is finished red with black five minute marks and white five minute numerals. This can be set with a second button. Dial & Hands: A black dial with rhodium plated batons, each two bright strokes with luminous paint between. There is a calendar aperture between 4 and 5 o'clock. The minute and hour hands are also rhodium plated and of skeltonised baton design filled luminous. The centre seconds hand is white. Movement: Ebauche Marks: None Frame: A plated nickel silver movement with a bridge for the barrel another carries the weight and contains the reduction gears for the self winding work. Beneath this is a further bridge for the train and another for the centre wheel. A cock for the pallets and another for the balance. Barrel and Mainspring: The barrel is marked 'Do not open' both in English and in French. Thus only external dimensions are given. Barrel: External diameter 11.0 mm., external height 1.4 mm. Hooking: A slipping mainspring. Train: All the brass wheels gilded, the centre, third and fourth wheels with five crossings. The steel escape wheel with four. Jewelling: Jewelled bearings from the centre wheel onwards, except for the idle centre seconds pinion. All the jewels pressed in. Shock protected bearings to the balance. Escapement: A straight line layout club tooth lever escapement with short lever, double roller and D-shaped impulse pin. The exposed pallet stones have flat acting faces. A steel escape wheel with four crossings. A mixed escapement. Solid banking. No. of teeth embraced 3½. Balance & Spring: a three arm monometallic balance with brass screws. Balance diameter 7.4 mm., thickness 0.45 mm. A 'self compensating' flat spiral spring with 14 turns. The stud is, most unusually, mounted beneath the cock. Means of Regulation: A micrometer regulator. The index on the balance cock has a yoked end embracing an eccentric screw - the slot of which registers against a divided scale with + and - engraved on the balance cock table. Train Counts and Beat Rate: Great wheel 85 (barrel) Centre wheel 72 pinion 12 Third wheel 75 pinion 9 Fourth wheel 100 pinion 10 Escape wheel 21 pinion 7 Beat rate 36,000 Motion work: cannon pinion 12 minute wheel 32, minute pinion 8 hour wheel 36 on which is mounted the calendar driving gear of 23 teeth which drives the calendar indexing wheel of 46. Self Winding System: Winding in both directions utilising rocking gears engaging with the reduction gear train. Winding System: Conventional positive stem set keyless work Dimensions: Case: Width 43.0 mm., length 41.0 mm., height 13.3 mm., (over the glass). Movement: Diameter 25.9 mm., height 6.7 mm. Provenance: Purchased in 1986 with the aid of funds made available by the late Stanley Burton. Note: An Ultrachron is shown in Marozzi, D. & Toselli, G. Longines Bologna 1990 p. 322. Although the same basic calibre it differs in many of its detail characteristics.