- Museum number
BLUED STEEL CASED DOUBLE-DIALLED TIMER.
Double dialled watch. Enamelled telemetric dials on both sides.
Blued steel case.
- Production date
Diameter: 56 millimetres (case)
Diameter: 44.20 millimetres (dial)
Thickness: 20.50 millimetres
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Mensor
Switzerland, c. 1905
Double dialled telemetric timer with a club tooth lever escapement.
Signature: On the dials 'Mensore DEPOSE'.(1)
Case: A gun metal case with a hinged back and a snap on bezel. The stem is retained by a screw in the pendant tube.
Dial and Hands:
The front dial: The dial at the front is marked out in a spiral fashion, the spiral being wound clockwise from the inside out. There is a centre seconds hand that revolves once a minute with, on the outside of the dial black seconds markings with the 5 second markings slightly heavier than the others. There are six turns to the spiral which has at its outer end the legend 'UNITS AND HUNDREDTHS'. The small hand that should register over the coloured segment is missing. This segment allows the user to judge which turn of the spiral the centre seconds hand is traversing, since the segment divisions are coloured and these colours match the numeral colours on each turn of the spiral. However the hands will continue to rotate after six turns have been accomplished and the small hand will no longer be over a coloured portion of the sector.
The hands will of course return to zero correctly after they have been stopped. This is a telemetric dial. The centre seconds hand is gilt.
The rear dial: The dial at the rear is similar to that at the front except that the hand travels anti-clockwise and the spiral is marked from the outside starting at 200 and finishes at the centre at 10. The same colour coding system is used as on the front dial. There are no seconds markings around the outside of the dial. This dial is for recording pulse rates. Both hands are gilt.
Both dials are cannister dials.
Movement: There is an adaptor ring for the movement which is secured in the case by three screws, one now with a broken head. The dials are snapped onto either side of this ring.
Ebauche Marks: On the inside of the front plate is the number 13560, on the front plate under the dial is the following: 'PAT. No 9685' the Helvetia cross '4649.7334. 8165' another Helvetia cross 'PAT OCT.2.94.'On the engraved balance cock is the Helvetia cross and the number 28430. Under each of the cocks, except for the pallet cock, is the number 560.
Frame: A gilded frame with a half plate layout. A bridge for the keyless work and the barrel, cocks for the fourth and the escape wheels. A combined cock for the centre seconds and revolution recording wheels. A bridge for the pallets and a cock for the balance.
Barrel and Mainspring: A going barrel with no cover, the barrel ratchet wheel acting as the restraint for the spring.
Barrel inside diameter 16.7 mm., height 2.1 mm
Mainspring height 2.2 mm., thickness 0.23 mm.
Arbor: Diameter 5.35 mm., snailed. The arbor is screwed onto a pivoted post.
Hooking: Pressed in from the barrel wall.
Train: The brass wheels are all gilded and have five crossings except for the escape wheel which has four crossings.
Jewelled: From the fourth onwards. Ruby endstones for the balance.
Escapement: A straight line layout, club tooth lever escapement short lever, double roller, an elliptical shaped impulse stone. The lever is gilded brass and is screwed onto the staff.
Adjustable banking pins.
An equal impulse escapement.
Number of teeth embraced 3 ½.
Balance and Spring: A monometalic balance but split(2) and with two platinum timing screws, the compensation screws brass. Balance diameter 15.9 mm., thickness 1.1 mm.
The flat spiral palladium spring with 14 turns and a terminal curve.
Means of Regulation: An index on the balance cock, the divided scale in black polished steel set into the cock with 'A R' engraved upon it. A further lever located by a shoulder screw has a forked end which acts on the end of the index and is accessible when the bezel is raised. The outer edge of the case middle is also marked with a divided scale and with 'S F'
Train Counts and Beat Rate:
Great wheel ( barrel) 80
Centre wheel 80 pinion 12
Third wheel 75 pinion 10
Fourth wheel 80 pinion 10
Escape wheel 15 pinion 8
The centre seconds wheel must have one of the longest slender arbors met with in watch work it is 14.14 mm. long and the main section is a mere 0.55 mm. in diameter, see ill. It has pivots at both ends so that both centre hands can be mounted on it.
Beat Rate 18,000
Motion Work: The cannon pinion serves no purpose as a gear but helps to provide a measure of safety for one of the slender centre seconds pivots.
Chronograph work: The levers are operated by a castle wheel which is in turn operated by pressure on the button. Near to the third wheel is a fine toothed disc A on an arbor which has serrated edges on both faces, one of these edges is in permanent contact with a serrated wheel mounted on the fourth wheel arbor. The centre wheel meshes with a pinion which carries a fine toothed disc with one serrated edge B, the pinion has 20 teeth. On operating the castle wheel the centre seconds wheel is allowed to move down so that it contacts the serrated disc A and the serrated edged disc B on the pinion that is driven by the centre wheel is allowed to move up so as to contact the revolution counter wheel. The next function is the stopping of the centre seconds wheel and the revolution counter wheel. The third function is the return to zero.
Winding system: Side set rocking bar keyless work but serving only to wind the watch as there is no hand setting involved in the operation of the watch.
Dimensions: Case diameter 55.5 mm., height 20.7 mm., over the glasses.
Adaptor ring diameter 44.4 mm., height 9.2 mm.
Movement diameter 42 mm., height 14.1 mm.
Provenance: Formerly in the Ilbert collection.
(1) See the Horological Journal for January 1903 where a similar watch is described and illustrated under the title 'The Mensor Speed Indicating Chronograph'. The reverse dial of the watch shows a conventional chronograph however, only the other being devoted to the speed indication function. Also there are only four coloured segments for indicating which circle one is on instead of the six on the version in the collections.
(2) The only purpose for the splitting of this balance must be to obtain isochronism by virtue of the action of centrifugal force on the balance rims. As the amplitude increases the rims will be thrown further out which will slow the balance vibrations. This can be made to counteract a tendency for the spring to cause the balance and spring to be fast in the long arcs.
- Not on display
- Latest: 3 (2017) not seen inside
- Acquisition date
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.1487 (Ilbert Collection)
Previous owner/ex-collection number: N303 (Ilbert Ledger)