I agree on the mid-1920s dating, but please know the two-screw extension stocks would come from roughly 5-10 years earlier. Contemporaneous extension stocks would have no medallions. Also, extension stocks like those are found almost exclusively on models with adjustable sights. On models with service sights, like yours, they represent an owner’s preference.

The part you want is a prewar I-frame hammer nose. You will also need a rolled pin (or a less authentic solid pin) to retain it. Check Poppert’s Gun Parts or Jack First Gun Parts. Or even eBay, where there is a flourishing parts and accessories trade.

Footnote: if you get the stocks off to look for the serial number, another identifier of the Regulation Police model will be a shallow step milled into the backstrap of the grip frame. This is part of the S&W design solution to mount smaller square-butt stocks than the ones on your gun now. These RP stocks are mounted with a single screw.

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David Wilson