In english:

Dear Sirs
I do not know if the photographic documentation was successful. From my investigation (from incompetente) the following writings and / or acronyms have emerged:
- On the cane. cal.6,5x57. GRUPP - LAUFSIAHLD
- Always on the barrel the symbol of a chaplet with letter N. And again St.m.G. 10gr.
- The abbreviation B.U.
- On the handle of the shutter the abbreviation B.U. 10635

As soon as I understand how to forward the photos, I will send them.
Peter