- Museum number
STAINLESS STEEL CASED AUTOMATIC WINDING CENTRE-SECONDS ALARM CLUB-TOOTH LEVER WRIST-WATCH WITH DAY-DATE MECHANISM AND STAINLESS STEEL BRACELET.
Movement with automatic winding and club-tooth lever escapement; stem wound alarm mechanism with on/off button in the case band which is also used for re-setting the date.
Silvered-metal dial with raised luminous-painted baton hour markers and day/date aperture; revolving ring around the outside with red and white indicator for alarm setting.
Stainless-steel hour, minute and centre-seconds hands.
Stainless-steel case with screw-on back.
- Production date
Diameter: 37.70 millimetres (case)
Diameter: 31.50 millimetres (dial)
Length: 270 millimetres (bracelet)
Thickness: 14 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Seiko
Japan, c. 1975
Self winding alarm wrist watch with day and date work and a club tooth lever escapement.
Signature: On the dial 'SEIKO BELL-MATIC 27 JEWELS JAPAN 4006 - 7050T AD'.
Case: A stainless steel case with on the outside of the back the Seiko trade mark 'STAINLESS STEEL WATERPROOF JAPAN J' and the numbers 4006 - 7020 and 878391. With the watch is a stainless steel bracelet with SEIKO on the buckle. The mating part of the buckle is marked 'ALL STAINLESS STEEL STL STELUX'.
Dial & Hands: Around the edge of the dial is the alarm setting ring a white triangle on a red rectangle marking the time the alarm is set to. The rest of the ring is faceted and finished bright silver. The brushed and silvered dial has batons double for the hours and triple for 12 o'clock. The baton centres are luminised. The minute circle is in black. The aperture for the day and date is situated at 3 o'clock the days being in English. On the back of the dial painted in black are the numbers 8. 7. There is a centre seconds hand.
The tapered baton hands are filled luminous.
On removing the main dial the day and date dials are revealed. The date numbers are in black and the days are in succession red, black and blue with the Sundays in red and the Saturdays in blue. The date dial revolves in two weeks. The day dial carries the number 870805T, mounted on the back of the dial is a star wheel with 14 teeth.
Ebauche Marks: 'JAPAN 4006A' on the self winding watch bridge.
Frame: On the self winding weight is 'SEIKO 27 JEWELS'.
Barrels and Mainsprings:
The Going Barrel: has a recessed cover.
Barrel I diameter 11.2 mm., height 1.0 mm.
Mainspring: height 1.0 mm., thickness 11.5 mm.
Barrel Arbor: diameter 2.95 mm, snailed.
Hooking: A slipping mainspring.
Alarm Barrel: I diameter of the recess that locates the spring 8.6 mm., height 1.4 mm.
Mainspring: height 1.4 mm., thickness 0.08 mm.
Barrel Arbor: diameter 2.8 mm, snailed.
Hooking: A notch in the edge of the centre wheel bridge restrains the spring.
Train: All the wheels gilded, the centre wheel, third and fourth wheels with five crossings. The steel escape wheel with four.
Jewelling: Jewelled bearings from the centre wheel onwards, with additionally both of the barrel arbor bearing holes jewelled at their lower end. All the jewels are pressed in. Shock protected jewelling for 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.
An equidistant locking escapement.
No. of teeth embraced 3½.
Balance & Spring: a monometallic balance with a plain rim. The balance is exceptionally light to give the greatest diameter for the given moment of inertia. Balance diameter 11.1 mm., thickness 0.42 mm. A 'self compensating' flat spiral spring with 13 turns.
Means of Regulation: An index on the balance cock registers against a divided scale with 'F' and 'S' engraved on the balance cock table. A beat setting device is fitted.
Train Counts and Beat Rate:
Great wheel 70 (barrel)
Centre wheel 80 pinion 10 The barrel and centre pinion have involute form teeth.
Third wheel 60 pinion 8
Fourth wheel 80 pinion 10
Escape wheel 15 pinion 8
Beat rate 18,000
Motion work: cannon pinion 15
minute wheel 40, minute pinion 8
hour wheel 36, the wheel with three raised nibs for the alarm set off.
Winding System: Conventional positive stem set keyless work.
Alarm Work: The alarm barrel is wound from the button. When the hour wheel allows the stop lever to rise and so to clear the alarm escape wheel teeth, the train can run and thus operate the hammer, which is integral with the pallets. These pallets span a mere two teeth of the escape wheel, which has 10 teeth.
Self Winding Work: The self winding work is mounted on a ball race. The weight carries a cam which rocks a double ended ratchet so as to index a fine tooth ratchet wheel. On tooth back ratchets over the ratchet wheel whilst the other gathers teeth. This fine toothed ratchet wheel carries a pinion which meshes directly with the barrel ratchet wheel.
Case: Diameter 38 mm., height 13.6 mm., over the glass.
Movement: diameter 31 mm., height 9.6 mm.
Provenance: Purchased in 1988 with the help of funds from the Dingwall Bequest.
- Not on display
- Latest: 2 (2017)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number