The gun you have is a 34sm. I'm not 100% sure of the introduction year but there are previous threads on.here related to them. I picked one up myself before last xmas. They are really good handling guns, and came complete with the scope you have with the gun. I have to say that the moderator is reasonably effective and I look forward to the day I can get around to a strip down and overhaul of mine. I suspect it will become quieter still and be an accomplished hunting weapon.
The 34s is a gun.I.also own.and is earlier again than the 34sm. This has a 15 inch barrel.
I think the sm only came in .22.

You will find a date stamp towards the rear of the cylinder above the trigger near the plastic end cap (month/year).
Glad for your fortunate acquisition.
Dave