Hi Jesse! Please stay away from any item from the Ukraine or Eastern European Country. There are very few genuine items that are coming from that part of the World, especially if they are on ebay!! Do your homework, read lots of books and trawl the internet. These are great ways to build up your knowledge. I do not think that there was a particualar Stoppuhr that was 'exclusively' used on a U-boot, but certain manufactures would have more likey been used than others. Unless you have a concrete history, it is always hard to confirm a true history of an item. I have a few watches on my site, please take a look: http://www.atlantik-pirat.com Happy Hunting! Max