Little confused as my 340B in 22 Hornet is made in Chicopee Falls (1938-1960) though has "SP" date code in an oval. No Serial Number, patent #2585798 (as best I can tell, which I think was issues in 1952 timeframe?). Exact marking is PROOF TESTED, with 22 - Hornet under that and Patent 2,585,798 (?) under that. top of barrel near receiver marked SP in oval circle, with 60F (?) under it. Any thoughts as to when this rifle was made? Thanks!