It was used in the Me-109 and other planes too.......https://www.google.ca/?gws_rd=ssl#q=...+borduhr+j30bz
JEDEM DAS SEINE
I don't think it is WW 2 German. If so it is quite different from the 2 or 3 that I have.
The case is surely postwar, but the clock itself is WW2. The clock is a 5th model of the pilot's clock called the BO-UK1, but the brass winding crown is from an earlier model and it is missing the dust cover in the back. Also the face with numbers erased may be a post war replacement.
Here is what I mean by the 5th model. I will show you how they evolved over time.
Here is the dust cover you are missing on the back. Dust covers were installed from the 2nd model and they also evolved in specs, but by the 5th model they were black or shiny aluminum.
Finally a comparison with the BO-UK1 used post war up until the 70s. On the right is the post war model, and I also show the plate on the postwar model. They were basically identical with the WW2 models of 1942, but the ring holding the glass became plastic instead of bakelite and the glass could also be plastic.
Here is a complete instrument panel from a Bf109 G10 I built up from original parts. See how the type 5 clock is installed.
From the 4th model the casing was also changed. Yours should be the type on the left. If it is the right one, now it means your clock was a 4th model or earlier with the wrong face (stopwatch part).
And here is the super rare type 6 model made in 1941 on the occasion of Junghans' 80th anniversary as presentation pieces. They were basically a type 5, but had the special feature of the Junghans logo on the face and was mounted on a wooden block with a Junghans plate in front. These are serial numbered in pencil under the block.