The Serial Number should appear in four separate locations on that revolver. Underside of the butt, underside of the flat under the barrel, rear of the cylinder, and underside of the extractor star. That is how one can tell if those parts were originally part of the revolver when it was shipped. However the serial number of record is the one on the bottom of the butt, and if has been made illegible it is a Federal offense to be in possession of the gun.
No way to confirm that, other than writing for a Factory Letter from Smith and Wesson. The cost of a letter is $50.
For what it's worth, Rufus Youngblood (1924-1996) was a Secret Service agent. He was on duty on November 22, 1963 when President Kennedy was assassinated. Youngblood was riding in Vice President Johnson's limousine, and when the shots rang out Youngblood vaulted over the seat and shielded Johnson with his body.
Although the revolver in question is clearly older than Rufus Youngblood, it is always possible he owned it at some point. A Factory Letter might or might not answer that question. If it did turn out that the revolver was owned by Rufus Youngblood, the Secret Service agent, it would have some collector's value because it was owned by a historical figure. If so, refinishing the gun would detract from its collector's value.
A long shot, but worth thinking about.