In close proximity to the odd maker's mark there is the stamp of Crown over N, STmG with 7/8 gr.

Then on the the lug, G(?). 16 . 8X72.

2.5 G.R. 5 K.M.G. - I think the 1st to be for powder and the 2nd for bullet weight? It is possible that it passed thru Collath's proof facility or the Frankfurt one.



Below the typical Eagle Crown over G, Eagle, Crown over U is
what looks to be 7,8mm with 72(mm??) below. And an odd makers mark about that.

Cheers,

Raimey
rse