Plus 3 for comments by Alk8944 and topsaddle. I spent two weeks at the factory in 1979 and agree with everything they said. I saw frames coming out of the molds and dumped into barrels. The steel that was poured into the molds came from the same pots. Model designations come much later in the process. My time was building model 64's and repair of many other K frames. There were actually some 64's chambered in 357 before the 65 was born. As far as the autos of that era - we only spent 2 days identifying issues and replacing parts. Not much smithing went into them. Even the instructors did not like the 39's and 59's.

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S&W factory revolver armorer