The Dirty Dozen. During the 40s, towards the tail-end of World War II, Britain’s Ministry of Defence (MoD) made custom orders from 12 manufacturers in Switzerland for military spec watches to equip its soldiers. Amongst them, were brands such as IWC, Longines and Jaeger-LeCoultre and they had to follow the strict specifications set out by the MoD.

The watches needed to have a black dial with Arabic numerals, to be waterproof and luminous, regulated to a chronometer level and composed of a rugged stainless steel case. Furthermore, they had to have fixed bars, have a broadarrow on the dial, signifying that it was the property of the government and also on the caseback which included other government serial numbers. Nicknamed the ‘Dirty Dozen’ by collectors, they were officially set out by the MoD as W.W.Ws, standing for ‘Watch, Wristlet, Waterproof’. The result was a group of 12 watches that embodied the very idea of ‘purpose-built’, and it doesn’t get any more utilitarian than this.

While it’s been mentioned that more prestigious brands produced W.W.Ws, right at the top of the heap and what is often the missing piece in a collection, is a little known brand called Grana. Powered by a simple manually wound, chronometer graded KF 320 movement, it looks like your typical military issued watch, but of course, with collecting, it all boils down to rarity as only 1000-1500 pieces were produced. Compared to others, they made 5 times as many IWCs and Longines, 10 times as many Jaeger-LeCoultres and 25 times as many Omegas!

You really do not see these coming up that often, this is the end game for Dirty Dozen collectors.