Help with proof marks
 

Greetings,
After all the years of collecting Lugers, you would think I would have seen it all. Today I received a Luger (52991) that I purchased last month from the Rock Island Auction. It has two very unusual proof marks that I would like some help on. Here are a couple of pictures. The first one is on the frame rail behind the side plate and the second picture is on the right receiver. Any help will be appreciated.
Thanks,
Mike

I do believe the "HZaJt16" marking is a stamp from a Heers Zeugamt army arsenal. The Jt stands for the city the arsenal was in (Jngolstadt). The 16 is what repair depot it was. From my understanding this is a stamp on a part representing it was replaced by the arsenal. I also have a luger that has that stamp on the sear bar of mine. I think mine has a different number at the end of it.

Ed Tinkers "Police Lugers" book talks about this stamp in it on page 15.