In 1970, the Defence Standard specifying chronographs changed to allow the use of mass produced, two button movements – and over the next 12 years four firms produced chronographs for the British military using the Valjoux 7733, allowing collectors to now call them the “Fab Four”.
Hamilton was the first to begin supplying them in 1970 through to 1972, followed by CWC from 1973 to 1982, with additional batches from Newmark in 1980 and Precista in 1981. Worn & Wound has a brief account of these watches here.
Most of the watches supplied had luminous dials with the NSN ending 9243306. However, CWC supplied at least two batches of non-luminous watches for use on nuclear submarines, with the NSN ending 9243312, in 1974 and 1975 (and possibly another in 1976 although only one watch has been seen from 1976 to date).
As the cases, dials and movements were all interchangeable, many of them became swapped around during MoD servicing, so it is not uncommon to find mismatched watches. In addition, serial numbers ran consecutively between brands, which makes tracing batches and serials numbers a somewhat inexact science. CWC produced around 3,500 of these watches in batches as listed below (I have written the NSNs as they are stamped on the case back).
1973: 0552/924-3306 in the 30xx to 36xx serial number range
1974: 0552/924-3306 in the 36xx to 40xx serial number range
1974: 6BB/9243306 in the 40xx to 45xx serial number range
1974: 0552/924-3312 around the 4050 serial numbers
1975: 0552/924-3306 in the 46xx to 51xx serial number range
1975: 0552/924-3312 around the 4710 serial numbers
1975: 6B/551-924-3306 possibly a batch of 50 or 100 numbered 001/75 to 050/75 or 100/75
1977: 6B/551-924-3306 probably a batch of 100 numbered 001/77 to 100/77
1978: 6BB/924-3306 in the 1xx to 25x serial number range
1980: 6BB-924-3306 in the 5xx to 7xx serial number range
1980: 0552/924-3306 in the 7xx to 10xx serial number range
1981: 6BB/9243306 which appears to be batch of 100 watches marked Bxxx/81
1982: 0552 924-3306 in the 15xx to 18xx serial number range
The 7733 has a central chronograph seconds, running seconds at 9 o’clock and a 30 minute counter at 3 o’clock. All the CWC dials were very similar, with a luminous 12 and 6, and luminous indexes, but there were four distinct dial types across the nine years of production:
1973 to 1978 ('Type 1'): The old logo without the oval; the numerals 2, 4, 8 and 10 are cut off by the subdials; the CWC logo is in line with the 2 and 10 numerals and the circled T is just below the top of the sub dials; the broad arrow is aligned with the bottom of the subdials. The non-lume versions in 1974 and 1975, are the same layout, but without the circled T and with no luminous material, of course.
1977 to 1978 ('Type 2'): Only seen on a few watches, in the higher serial numbers of 1977 and the lower serial numbers of 1978; the CWC moves slightly upwards on the dial to create a bigger space between the logo and the circled T, and both the CWC and the circled T are printed in plain white.
1980 and 1981 ('Type 3'): The numerals 2, 4, 8 and 10 are now only just touching the subdials (although it could be argued that the 8 is slightly cut off by the subdial); the CWC logo moves back down to be in line with the 2 and 10 numerals and the circled T moves up to be in line with the top of the sub dials, meaning these watches have the logo and the circled T closest together of all the variants; the broad arrow becomes bigger and moves down the dial to just below the 4 and 8 numerals.
1982 ('Type 4'): The new logo in the oval is added; the 2, 4, 8 and 10 numerals are now all clear of the subdials; the circled T moves down to just below the top of the sub dials; and the larger Pheon moves up to be in line with the 4 and the 8.
In the 1970s, the hour and minute hands were “syringe” type, with slightly rounded ends, and the central chronograph seconds hand had a pointed tip, and was straight and squared off at the other end. In the 1980s, the hour and minute hands changed to pointed “pencil” type, and the seconds hand was flat at the tip and flared slightly to a flat end at the other end.
The other notable difference is in the NSN on the case back - the 1970s watches had deep, large stamping, whilst the 1980s watches had smaller, etched NSNs on the case back.
There were also slight changes in the dial printing over the years – the 1980 version has a silver gilt logo, circled T and broad arrow, whilst the 1982 is all white printed, for instance.