- Museum number
BASE-METAL CASED SUBSIDIARY SECONDS CLUB-TOOTH LEVER TWO-DAY DECK WATCH WITH UP-AND-DOWN DIAL IN ORIGINAL GLAZED MAHOGANY BOX.
Movement with nickel-silver plates, cocks and bridges.
Club-tooth lever escapement with monometallic balance and Ni Span C balance spring.
Silvered-metal dial with Arabic hour numerals, subsidiary seconds and state of wind indicator.
Aluminium case with screw-on back and snap-on inner cover.
Keyless winding and hand-setting.
Housed in mahogany box with hinged glazed lid; lined with green baize; applied metal plate on lid inscribed with operating instructions.
Complete with spare click spring, hand-setting push-piece and three screws.
- Production date
Diameter: 70.50 millimetres (watch)
Height: 5.40 centimetres
Length: 15 centimetres (box)
Width: 12.50 centimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Hamilton Watch Co.
Boxed and aluminium cased deck watch with a club tooth lever escapement.
Signature: On the barrel bridge "HAMILTON WATCH CO MODEL 22-21 JEWELS ADJ. TO TEMP & 6 POS. MADE IN USA. US NAVY - BU SHIPS - 1943". On the dial "HAMILTON LANCASTER, PA, USA"
Box: of mahogany, not lockable but with a catch on the front. A glazed circular aperture in the hinged top reveals the watch. The piano type hinge is chromium plated and retained by Phillips screws, as is the catch. On the recess in the top is screwed an engraved aluminium label which reads as follows:-
CAUTION ALWAYS KEEP WATCH IN HORIZONTAL
(DIAL UP) POSITION TO ASSURE
TO SET WATCH (HOURS AND MINUTES ONLY)
1. Depress shielded safety pin on edge of case
2. Keeping pin depressed, pull out crown
3. Release pressure on pin and set hands
4. Push crown back to winding position
(Safety mechanism relocks automatically)
WATCH CO PENNA
The interior of the box is lined with cushioned green baize.
Case: Aluminium open face case. In the screw on case back is "KEYSTONE and Co" in a keystone surround, "BASE METAL" and the number 570499. A map on inside back cover. Screw on bezel.
Dial and Hands: Metal dial, silvered, with Arabic numerals. A subsidiary Up-and-Down and seconds dial. The up-and-down dial numbered 8, 16, 24, 32, 40, 48 and inscribed "UP" and "DOWN". Blued-steel spade hands. Blued-steel up and down and seconds hands.
Ebauche Marks: The front plate numbered 2F 27246
Frame: In appearance a bar layout but the train has in fact a single bridge machined to resemble 3 bars. The watch is designed to run for 56 hours.
Barrel and Mainspring: Going barrel I diameter 23.25 mm., height 4.2 mm.
Mainspring: height 4.1 mm., thickness 0.2 mm., this marked HW Co (see note 1)
Arbor: diameter 6.3 mm., snailed
Hooking: T piece and brace
Train: Brass wheels gilded with five crossings except for the steel escape wheel which has 4. The pinion leaves are exceptionally well finished.
Jewelled: From the centre onwards, unusually both the top and bottom centre holes jewelled. All the jewels are friction set in chatons except for the centre in the front plate. Ruby endstones to the escapement.
Escapement: Club tooth lever, straight line layout, short lever, double toller, the impulse roller brass, the safety roller steel, impulse pin D shaped. Pallet stones exposed. Escape wheel steel, both the impulse and locking planes burnished.
An equal impulse escapement.
Number of teeth embraced 3½
Balance and Spring: Bimetallic uncut ovalising balance, the bar of invar the rim stainless steel, gold compensation screws, quarter timing nuts of platinum. Balance diameter 20.5 mm., height 1.75 mm. Ni-Span C flat spiral spring with 12½ turns and a terminal curve. The brass collet is poised.
Means of Regulation: Micrometer controlled. An index on the balance cock is biased by a spring against a cam which is mounted on a divided disc with "F S" engraved on the cock.
Train Counts and Beat Rate:
Great wheel 96
Centre wheel 75 pinion 12
Third wheel 80 pinion 10
Fourth wheel 80 pinion 10
Escape wheel 15 pinion 8
Beat rate 18,000
Motion work: cannon pinion 12
minute wheel 36, minute pinion 10
hour wheel 40
Keyless work: Positive set keyless work with a device patented by Ernest W. Wescher. This has a safety catch which needs to be pressed before the stem is put into the hand-set position, only then can the hands be set. This prevents accidental handsetting.
Up and Down Work: Planar differential work.
Dimensions: Box: Width 125.4mm., length 151.80mm., height 54.1mm
Case: diam 71.0 mm h. 22.0 mm.
Movement: diam 59.0 mm h. 13.0 mm over glass.
Provenance: Presented by the company to the Managing Director of Hamilton (UK), Mr Raymond Mellor, in 1962. Then purchased in 1988
(1) The barrel and mainspring design is unique to this watch. At first sight the spring seems to be incorrect since it fills so much of the barrel, far more than theory allows, however following theoretical considerations simply gives the maximum torque output possible for the available volume of the barrel which has nothing to do with the uniformity of torque output. The classical rules were in fact formulated for the fusee/barrel combination where maximum available torque is the aim, since the fusee is then used to equalise the torque output. With the going barrel the only way to equalise torque output is to utilise the intercoil friction, which is at a maximum when the spring is fully wound and diminishes as the spring unwinds. The ratio of intercoil friction to torque output depends upon the thickness of the spring. The thinner it is made the great the frictional losses. This then is the reason for the thickness of the spring being a mere 0.20 mm whereas one would expect it to be about 0.26 mm. for this size of barrel. Ultimately then maximum torque is sacrificed for uniformity of torque output.
One factor that cannot show in a pure torque/turns test is the effectiveness of the pull of the mainspring as a rector. In the extreme case if the pull was radial no torque would be delivered at all, it would all be wasted. Thus the aspect of the spring in its barrel is important. In the case of the Hamilton barrel it is as favourable as it can be since, due to the amount of spring in the barrel, it never goes far from the barrel wall even when fully unwound. The same effect would be produced by making the barrel arbor bigger. The provision of a brace also helps in this direction.
(2) It is of interest to make a comparison with the Paul Ditisheim Deck Watch, registration no. 1972,0903.11. The relevent dimensions (in mm) are as follows:
Barrel Diameter 23 23.25
Spring Thickness 0.24 0.20
Spring height 5.0 4.1
over rim 20.0 17.3
over screws 22.5 20.0
Balance height 1.825 1.75
- On display (G39/dc10)
- Exhibition history
2008 Feb 1-Apr 16, Liverpool, Prescott Museum, 'Lost Time'
- Latest: 2 (Sep 1995)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number