Another riddle

[cel7]

At an auction I won a rifle that turned out to be the worst buy of the year (should I make even worse purchases this year, I'll take these words back). Because of the distance, I took the gamble and didn't go to the auction house to see it in person. It was stated on the website that the stock was broken, that it was falling apart into several pieces when I tried to disassemble it, I did not expect . A wise lesson learned: when in doubt, just go and see for yourself or don't buy.

I bought it because I suspected it was a military rifle (due to the presence of a bayonet catch and because it has few decorations). At the moment I'm not quite sure what it is or rather "was". It looks like a kind of "jägerbuchse" with a heavy octagonal barrel with 7 spiral grooves (Minië system?)
The gun is unmarked at first glance, except for a number on the chamber and a unknown stamp op the stock. Take it apart and find the same mark or perhaps proofmark on the underside of the barrel, the stock, trigger guard, and on the inside of the lock, in the form of an upward arrow and a 5. Unfortunately, I have no clue about origin of this gun. Anyone have an idea?