Hello Wulfpak,
I suggest you try to do research through the Manufacturer first, then
www.uboat.net re Nr. 1225.
The stopwatch during those times had many uses. i.e., the Funkmaat would receive radio time hacks and transferred to the watch which the steuermann would use for making a round of stars with the sextant. Correct time was/is essential for accurate navigation (Longitudes).
Here's a site that might help:
http://aa.usno.navy.mil/faq/docs/celnav.html
As you know already, the watch is used for timing the torpedo run, and timing the distance between target bearings.