Sounds like a S&W version of the
Maltese Falcon....hopefully it turns up on this forum...
Right when you think you know S&W 5 screws......you hear about a 22 LR RM!!!!
Like many other long lost treasures, (Bugatti type 57 Atalante found in England) some older man, in his 80s to 90s probably owns it in his vast gun collection and has no idea as to its modern day value or its historical importance or rarity.
Just some large 22 S&W he bought in 1957 off a guy...