- Museum number
Nickel-chrome Plated Wrist Watch.
Nickel-chrome plated case with fixed strap lugs, snap-on back and bezel, the latter divided to seconds and numbered 5-60.
Black-painted dial with an outer minutes circle and hours 1-12, numbers 3,6,9 and 12 luminous painted. Blued-steel hour and minute hands, red-painted metal centre seconds hand.
Seven-jewel movement with club-tooth lever escapement.
- Production date
Diameter: 48.50 millimetres (bezel)
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Seikosha
Wrist watch with centre seconds and a club tooth lever escapement.
Signature: On the Train bridge 'SEIKOSHA'.
Case: A round chromium plated three piece case with a snap on back and bezel; the bezel serrated. On the outside of the back are some Japanese letters but the back is so worn it is not possible to decipher these.
Inside the case back is stamped an anchor, SKS in a cartouche and another mark not deciphered. A moveable seconds ring, the minutes in red, surrounds the main dial and has the five seconds (or minutes) in white.
Dial & Hands: A black dial with white Arabic numerals, the 12, 3, 6 and 9 larger and luminised. The minute circle also in white with luminous dots every five. Bright steel spade hands and a red centre seconds hand. The dial is secured with three side screws.
Ebauche Marks. On the dial plate under the dial are the numbers 184 and 04 inside is the number 5.
Frame: A round movement with nickel plated brass plates and with a Geneva stripe finish. A bridge for the barrel keyless work and the centre and third wheels and one for the other two train wheels. A bridge for the pallets and a cocks for the balance and the centre seconds pinion.
Under the bridges except for the pallet bridge is the number 184 and additionally under the barrel bridge is 04.
Barrel and Mainspring:
Going Barrel: I diameter 16.8 mm., height 2.9 mm.
Mainspring: height 2.8 mm., thickness 0.19 mm.
Barrel Arbor: diameter 5.8 mm., snailed.
Hooking: A brace is fitted which locates in slots in both barrel bottom and cover.
Train: All the brass wheels are gilded, the centre, third and fourth wheels with five crossings. The steel escape wheel with four.
Jewelling: Jewelled bearings at the balance with ruby endstones. The jewels rubbed in to chatons with the plain holes also in chatons.
Escapement: A straight line layout, club tooth lever escapement with short lever, double roller and D-shaped impulse pin. A steel escape wheel with four crossings. Exposed pallet stones, the acting faces flat.
A mixed escapement.
No. of teeth embraced 3½.
Balance & Spring: A split bimetallic balance with brass compensation screws and two timing screws. A 'self compensating' balance spring. Balance diameter 17 mm., thickness 1.25 mm. A flat spiral spring with 14 ½ turns and a terminal curve.
Means of Regulation: An index on the balance cock registers against a divided scale with 'F S' engraved on the balance cock table.
Train Counts and Beat Rate:
Great wheel (barrel) 80
Centre wheel 80 pinion 12
Third wheel 75 pinion 10
Fourth wheel 80 pinion 10
Wheel driving centre seconds pinion 90
Centre seconds pinion 12
Escape wheel 15 pinion 8
Beat rate 18,000
Motion work: cannon pinion 10
minute wheel 30, minute pinion 8
hour wheel 32
Winding System: Negative set keyless work.
Dimensions: Case Diameter 48.2 mm., height 17.7 mm., over the glass.
Movement: Diameter 42.8 mm., height 11.0 mm.
Provenance: Donated by Imai Kesaharu in 1996.
1. For a small seconds version of this movement see registration no. 1996,1204.1.
2. The punched marks inside the case are an anchor and a 'To' showing that the watch was was accepted for use by the navy and that it was checked by an inspector from the Tokyo office.
3. The outside of the case is inscribed with a series of Japanese characters:-
The top left character "hei" which means soldier or sailor and the top right character is "Kuu" meaning sky - the Japanese navy way of saying pilot.
Verticallydown is the number 7788 and the bottom character is 'Gou', a suffix which usually follows all numbers such as this.
All watches were inspected before acceptance at a certain standard by the navy.
- Not on display
- Latest: 3 (Mar 2000)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number