The lag of date stamp indicates a pre-WWI production, that stamp became mandatory in 1912. It is also not stamped with the /70, so it's chambered for 12/65 (2 1/2"). Don't fire it with 12/70 shells even if they seem to fit.
I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.