That model originally had a pinned barrel which was eliminated in 1982 along with the counter-bored cylinder and was stamped 629-1. Your revolver was probably produced right at the time of the changes and was built without a pinned barrel but did get a counter-bored cylinder. This is common with some engineering changes, they may mandate the change but they're not going to throw away any counter-bored cylinders and etc. that they may still have. Your revolver could have been built with a pinned barrel and a cylinder that wasn't counter-bored. As for the price, it sounds like full bore but if you're happy, that's all that matters. Anyway, enjoy that great piece!