Cool marking! Never seen one like it. I always thought the Roman numerals were divisional staff markings

 

Found it! This is in Jeff Nolls Imperial German Regimental Markings Addendum 2nd Revision:

 

Hello Chris, Thanks for info. Evidently this is a known pistol, as that is the serial number on mine, plus what looks like an "a" partial stamp on the frame. Will print out and keep with pistol.
While I probably have over 40 Luger books, not familiar with Mr. Nolis book. Oh, boy, new search.
Thanks again, Skid

 

Jeff Nolls is a member here. IIRC a link for his books are listed in the trader section.

NICE PISTOL!!! I'm jealous. I recently just missed a 13 Erfurt also marked to an MG unit. I asked too many questions.

 

I just picked up a 1912 Erfurt, no unit mark on the gun but the holster appears to have a Train Division unit marking on it.

 

Hello Fireman11, Got this from a local fellow collector who is thinning out. As I mentioned, I have a 1913 Erfurt, so one without and one with lug a year apart. Will check the trader, Thanks.
Hello Herrkaiser, Very unique holster.
Skid