Finally, a light comes on! Here's what I've discovered thus far. I now understand why the watch was listed by the auctioneer as being "Sherman tank watch". Thanks to an old Britishicon soldier, I found out that some radio sets had the provision for mounting a pocket watch on the face. It was a 2 pc. black ring, the back of which was screwed to the face of the left of the radio set and the front piece threaded on to it. The watch would be wound, put in the holder, and then the face ring threaded on. Presumably, this watch came out of the estate of some veteran Armoured Corps radio operator (hence the Sherman tank attribution). From the pics I've managed to find, there were many different models of watch used and not all were "sterilized". I'm hoping that when I get full access to a military watch collectors site I joined, I'll get all the information I need. Here's a pic I managed to download.