When did S&W start putting the serial number under the yoke?

There is probably a barge load of revolvers with the butt number covered by grips and with the "fitting number" on bill of sale, 4473, CCW, etc.

Victory models also had the serial number stamped on the flat underneath the barrel. Don't know if civilian guns did or when they quit.

After model stamping started in about 1958, revolvers with factory Target stocks had the SN in the yoke recess. This seemed to evolve to most Target sighted guns, then many others unpredictably. Only later J frames started having them due to space constraints.

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Alan
SWCA LM 2023, SWHF 220