I attended the auction at the symposium and these stocks were offered but no one was sure what they fit. I assumed that they would be 41 or 52 if they were donated by a S&W enthusiast, and it was for a good cause so I'll take a chance .When I got them I saw that they required 4 screws so I'm still thinking 52, but I couldn't rule out 1911. The big gorilla also thought 52. I finally got around to trying them and was very happy with the result.