"The Dirty Dozen" is also watch collector's slang for a particular set of vintage wristwatches. In 1945, the British MOD (Ministry of Defence) decided that it needed wristwatches for a number of military occupations, and that current watches easily available on the civilian market were not accurate or durable enough. As a consequence, the MOD drew up a set of requirements, and invited any Swiss company that could meet the requirements to provide watches. Twelve (or thirteen, according to some sources) responded.
The watches were all designed similarly - metal cases, with pigskin or canvas bands. They sported black dials with white Arabic numerals and a 'railroad track' minute marking around the outside. All markings and the hour and minute hands had luminescent marks. Time was indicated on the main dial by minute and second hands, with a separate sub-second dial in the lower half of the face. They were hand-wound, not automatic; and they were required to meet a strict accuracy requirement. They had to be waterproof, use between 15 and 17 jewels in their movements, and to use shatterproof Perspex for their crystals.
Once in military service, the watches were designated (and marked on the back) "W.W.W." which stood, in classic military-speak, for "Watch. Wrist. Waterproof." Over 150,000 of these watches were purchased by the U.K. military in varying numbers from the twelve difference manufacturers. Why Swiss? Remember, British industry was not only heavily disrupted after World War II, but British watchmaking had apparently never really managed to make the jump to industrial production, remaining in a more cottage mode with watches being handmade or shop-made. Many British instrument makers had, during the war, retooled to make aviation instruments, artillery calculators, and other specialized mechanical devices. In 1945, it just wasn't practical to procure many thousands of watches, built to a high standard and nigh-identical, from the British Isles.
Oh right. I said 'twelve different manufacturers.' They were, by name:
Hm, I said 'thirteen' above, though, right? Right. There are stories that mention another company, called Enicar. No watches are known to have been delivered by or accepted from Enicar, however. I don't know why - there are various stories that the Allies determined that Enicar was supplying customers that they disapproved of - although I'm not sure how true that is. Switzerland was of course supplying the Nazi regime, as a neutral, during the war, which means likely all firms would have been guilty of that. Perhaps they were trading with the Soviet Union? Who knows. Perhaps they were just unable to manufacture watches to the required spec.
The watches were marked with the 'W.W.W.' designation on the case backs; they had two serial numbers, one from the manufacturer and a military serial number as well. In addition, they had a distinctive marking - a broad arrowhead, or the Broad Arrow, used by the British Government to mark its property. Generally, each watch was originally shipped with the maker's name between the center and 12-o'clock position, with the Broad Arrow directly below the name and above the center. Later on, however, as the watches were refurbished by the MOD's REME (Corps of Royal Electrical & Mechanical Engineers), they were not only mixmastered - parts were mixed between watches where they would function - but the dials and some case backs were replaced with spares which contained military designation numbers but no manufacturer's mark.
Today, it's considered a 'grail' achievement to collect one from each of the original twelve manufacturers in original condition. Finding individuals isn't that difficult, but there are a couple of problems which make complete sets vanishingly rare. First, the aforementioned refurbishment means the number of 'original condition' units is lower. To make things worse, it seems that since the luminescent markings were originally done with radium-226, a large number of the watches were destroyed in the 1970s for safety reasons. And finally, a few of the manufacturers only made a few thousand each - so for example if you find a Grana, and it's affordable, buy it - because only maybe 6,000 of those got made, and collectors need those like Monopoly players need Park Place.
I learned about these watches while trying to identify a watch I recently purchased. It's marked as an Omega Seamaster Automatic, and was advertised as a 1952 bumper automatic from that company. I was becoming worried I'd bought a fake, or a total frankenwatch, as I was unable to find any images of any watches which matched mine. A few knowledgeable folks on the internet, however, have convinced me that what I in fact have is an actual 1952 bumper Omega Seamaster which has been redialed with a custom-painted dial. My dial looks almost exactly like the Dirty Dozen Omega dial - except instead of the Broad Arrow below 'Omega' and their logo, mine says 'Seamaster Automatic.' In addition, mine is a bumper - and the originals were all hand wound, and in the case of the Omegas, were calibre 30T2 movements, instead of the calibre 342 or 344 I'm pretty certain is in mine. Someone, clearly, wanted an automatic that looked like one of the Dirty Dozen, and had this one modified to match. I'm going to guess it's an original Seamaster dial, repainted from white to black with the appropriate markings added atop.
This hasn't made me upset. On the contrary, I kind of love my watch more. I bought it not to collect, but because I loved the way it looked, and to wear it - and it appears I have an even rarer watch than I'd thought - maybe a unique one! My hipster side can smugly note that, well, no, you don't have one like this, whoever you are.