Many years ago I made a switch with my friend. I got this and he got air rifle.Itīs measures are (if I remember right) approximately 60*60 cm. I donīt find any markings but same number in many parts #5 or something. Itīs not younger than 1950, because my friends father was in the army as a diver and he bring it home. I have good reason to believe that it is Finnish, German or Russian. Nobody any ideas or knwledge about this?