I just stumbled onto this:
http://www.p38guns.com/HzAStamp.htm
I will have to get a copy of the book...
Anyone know if it is a WW2 era marking or if it was already in use during WW1?
The upper half (which is marked HZA) is in such pristine shape, its hard to believe the pistol needed any repairs. Unless maybe the work WAS to stick it onto another frame.