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That said it is a J or small frame .38 Special. If it has a steel frame it is a Chiefs Special, and an alloy frame a Chiefs Special Airweight. The hammer has been "bobbed" (spur removed).
We need the number of digits in the SN, and any letter(s) in it. Serial number 399 would be from 1950, and 399000 1964. If the stocks and other visible parts are original it could be from anywhere between the mid-1950s and the mid-'60s.