CWC supplied a number of different types of clocks to the MOD, both with and without CWC branding on the dial; the original name of the business was, afterall, the Cabot Watch & Clock Company!
Just as the Navigator wristwatch replaced the HS3 deck clock in 1980, the HS1 marine chronometer and the HS2 chronometer watch were replaced by a quartz crystal chronometer with the NSN of 6645-99-541-7361 (as a reminder, the Navigator NSNs end in 7362 and 7363 for luminous and non-luminous watches respectively).
These boxed chronometers do not have CWC on the dial, probably because there is no allowance in the DefStan (published 19th June 1981) for a brand or trade mark on the dial, which specifies the dial as:
"The dial shall be made of an appropriate non-magnetic material. It is to be matt black with matt white numerals and graduations, in accordance with Fig 1." The DefStan for the quartz G10 from 1980, by contrast, states that "The trade name or trademark may appear on the dial above the centre."
However, Ray has said he supplied "boxed chronometers with quartz movements, and also brass bulkhead clocks with a quartz movement", and given that these date from 1980 and 1982 when CWC was supplying tens of thousands of quartz watches to the MOD, these can be confidently attributed to CWC.
The DefStan specifies that the movement accuracy should be plus/minus 0.25 seconds per day at 20 degrees centigrade, boxed in a hardwood case with a protective satin polish, capable of providing protection from accidental splashing by water. Hands, dial, and fittings should all be non-magnetic. A stop/start device shall enable the centre seconds hand to be synchronized with a time standard ("hacking" function"), and with the movement running, the hour and minute hands must be able to be set to time, without affecting the centre seconds hand.
Examples have been seen from 1980 and 1982, with some from 1980 also marked 6BB (for the RAF). There is also a type with a hinged back to the wooden box, apparently only issued to Submarines according to the original specification which is still held by CWC.
As well as the boxed chronometers, CWC supplied brass ships clocks, clocks designed to be for securely mounting in to a bulkhead or working surface, and grey metal deck clocks.
Figure 1 from the DefStan for Chronometer, Electronic, Quartz showing the general dial layout of the clock.
Chronometer from 1980.
Chronometer from 1982; this appears to have been used as a one of a set of chronometers, potentially showing different time zones (in this case, Greenwich Mean Time).
The DefStan states that "The following NATO Stock Number shall be marked on a metallised lable which is to be attached to the case of the chronometer: 6645-99-541-7361." Maybe 50 of the chronometers in 1980 were marked 6BB for the RAF.
NSN and issue number for the 1982 clock.
Instructions for battery replacement and how to hack (stop) the centre seconds when setting the clock, in line with the specification in the DefStan.