I have this JC Higgins Model 60 12 gauge that someone gave me. It also has 583.66 stamped on it. It's in pretty good shape. I haven't shot it yet. It has a vented piece with a dial on the end of the barrel that I'm assuming is a type of brake and spread adjuster. I think it's missing one of the cartridge stops. It has one of them, I'm just not sure if it's supposed to have both of them. I'm thinking that's why the cartridges won't stay in the magazine tube... Just wondering if anyone has any idea what this thing is worth??..Any info is greatly appreciated.