It's a Swiss army issued rifle of (I'm guessing) WWII or immediate post-war vintage. Military service was compulsory for all able-bodied Swiss males who were then required to keep their weapons at home in the event of an emergency mobilisation (I'm not sure if the laws have changed with respect to taking home armaments!). The bayonet was in a leather scabbard which I unsheathed, then fixed to the muzzle.
Impressively, the bayonet was sharp and glistening even after at least 40 years in the cellar (the former tenant passed away in his 90s, I'm assuming the gun was his and that he wouldn't have had to report his weapon or maintain it after the end of his service days in his 40s). Military steel, there's nothing else quite like it!