Guns with the "O" prefix

[Hammer Gun]

I have a wild guess about the prefix guns, Were the O prefix done during a certain time period and the A during a certain period, same with the B and so on. I have A1943 which is a 32" Damascus 12 bore Back Action, O Prefix up to Ser# 1000 and A Prefix up to Ser 2000 B up to Ser 3000, give me some feed back, and lets put some numbers out of early back action guns, Gary

[Scott Fox]

I have O1416, Back action W/ Decarbonized Barrels.

[Jim DiSpagno]

serial # 2422 preceded by a B