The .38 S&W post war I frames were reintroduced c. 1948 at # 54475. So yours would have to be 1948-49. It's a very early one with the leaf main spring/tension screw in the front grip strap and the round butt Service Stocks (round tops). The Improved I frame (w/coil mainspring) did not begin until # 62,381, on 7/9/51.

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Jim
S&WCA #819