Originally Posted by JP@AK

sikacz
That is a pressed stud, not a threaded stud. The pressed studs are not all polished flush like they should be. Some look like yours and others are darn near invisible.

The change order to replace the threaded stud with the pressed type was issued on January, 18, 1946, and the change was implemented shortly thereafter. By 1947, it appears that all K frame revolvers were fitted with the pressed studs.

I would have no idea where you could get a replacement stud, nor how to R/R the one you have. Others here may be able to address that part of your question.