Stainless-steel cased self-winding lever wrist-watch with stainless-steel expanding bracelet

Description — British Museum

Wrist-watch. Twenty-one jewelled movement with automatic winding and lever escapement. Black metallic dial with stainless-steel hour batons and a circle for the minutes marked every fifth minute with a luminous-painted dot; rectangular aperture to right shows day of week and date. Stainless-steel hands with luminous-painted bands. Stainless-steel case with screw-on back. Stainless-steel expanding bracelet.

Curator's comments — British Museum

Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript) Made by Seiko Watch Co. Japan, c. 1960 Self wound wrist watch with day date and a club tooth lever escapement. Signature: On the dial 'SEIKO' and the Seiko trade mark also 'AUTOMATIC 21 JEWELS JAPAN 6119 8160T AD'. On the self winding bridge 'SEIKO 21 JEWELS JAPAN 6119B'. Case: A two part stainless steel case with a screw back. On the outside of the back is 'SEIKO STAINLESS STEEL 6119-8160 WATER PROOF 802285 JAPAN. J'. The sight ring is black and has minute marks. At the five minute marks there are luminous dots. Dial and Hands: A grey dial with rhodium plated batons filled with luminous paint. An aperture for the day and date indication with its surround rhodium plated. The day dial is printed in English has the inscription "C RING" which is repeated in Japanese and the number 870 610 T", it is only 0.075mm. thick and is finished silver with a black days of the week but with 'SUN' in red. The dial ring for the dates is in black with white numerals. Rhodium plated baton hour and minute hands, skeletonised and filled with luminous paint. The rhodium plated centre seconds hand has a skeletonised tip also filled luminous. Movement: Ebauche Marks: none. Frame: A nickel silver movement. A bridge for the barrel and another for the train, a cock for the centre wheel, a bridge for the pallets and a cock for the balance. Barrel and Mainspring: A recessed cover to the barrel. Barrel: I diameter 11.2 mm., height 1.0 mm. Mainspring: height 1.0 mm., thickness 0.09 mm. Barrel Arbor: diameter 2.8 mm., snailed. Hooking: A slipping mainspring with the outer turn of the spring reinforced by a single turn of thicker spring. Train wheels of brass, gilded. The centre, third, and escape wheels (this latter steel) with five crossings, the fourth wheel with six. Jewelled: from the centre onwards the jewels pressed in, endstones to the escape wheel. Shock protected bearings to the balance of the KIF type but known in this watch as the "Diashock Shock Resistant Device". Escapement: A straight line layout club tooth escapement, short lever, double roller, the impulse pin D shaped. The pallet stones exposed with flat acting faces. The escape wheel of steel. Solid bankings on the pallet bridge. A mixed escapement. Number of teeth embraced 3 ½. Balance & Spring: a four arm monometallic balance with brass screws. Balance diameter 11.7 mm., thickness 0.4 mm. A 'self compensating' flat spiral spring with 13 ¾ turns. Means of Regulation: An index on the balance cock registers against a divided scale with + and - engraved on the balance cock table. Train Counts and Beat Rate: Great wheel 84 (barrel) Centre wheel 75 pinion 12 Third wheel 64 pinion 8 Fourth wheel 96 pinion 10 Escape wheel 15 pinion 8 An unusual train. Beat rate 21,600 Motion work: cannon pinion 12 minute wheel 36, minute pinion 8 hour wheel 32 Self Winding System: The weight runs on a ball race and is eccentrically mounted. It carries a ratcheting lever which has click terminations that, as the weight revolves, alternatively pull and push on the fine tooth ratchet wheel. This latter wheel carries a pinion which meshes directly with the barrel ratchet wheel. Day and Date work: the hour wheel of 32 drives a pinion* of 16 so that this revolves once in a ¼ of a day. This pinion is integral with another of 12 leaves which in turn drives the calendar indexing wheel of 48, thus this revolves once a day. A cam* on the indexing wheel propels the date ring. * In registration no. 1986,0509.2 these two pieces were made of a plastic material. Winding System: Conventional positive stem set keyless work but there is no winding pinion so no provision for manual winding, only hand setting. Dimensions: Case: Diameter 38.0 mm., height 11.3 mm.(over the glass) Movement: Diameter 26.7 mm., height 7.5 mm. Provenance: Purchased in 1986 with the aid of funds provided by Stanley H. Burton. Note: for an almost identical example see registration no. 1986,0509.2.