Ray is correct: the D ... H points to a post-1932 German military watch. The D...H stands for "Deutsches Heer" or German Army, and even though it was later called the Wehrmacht, this usage remained. Post-1945 that changed.
My sinister reputation seems to be spreading.....!!
Lovely watch! I can add little to what my knowledgeable pre-posters have said. Mainly the serial number, pointing to the late thirties or early forties (i.e. German army, pre-1945, as already stated) and the movement: something out of the Cal. 18-28 series. Since it is a lepine movement, it should be 18-28-1 or 18-28-3. It might also be a 19-28 - the first two figures denote the movement size (18''' or 19'''). Compare:
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