I am being a wet blanket but there is no such thing as a factory 1950 square butt D.S.
The Colt historian, Beverly Haynes, nor her asst. Joe, have ever seen one nor have they ever unearthed a factory letter for a custom order one.
Even without seeing this gun I don't believe it's factory original.
The only Detective Specials ever verified as being factory square butt after 1933 were about 5,000 that the US govt. ordered for Army Intel, Army Counter Intel, Army C.I.D., Naval Intel, the OSS, and supposedly some few for the Postal Service. These were ordered and filled from 1942-1945 and they letter specifically as 2 inch barrel square butt Detective Specials with specific military addresses and sometimes a base commanding officer as the recipient.