Very nice!.
Just viewing the pictures, it appears to be a couple of different karats of gold plus perhaps platinum for the inlay work.
Sterling silver tarnishes and turns black over time,,.99Fine silver retaines it's color pretty well but is more white than the grey tone color of platinum.
Just guessing of course...
A first rate job.
..and someone would have had to do the Factory style polish & bluing (again?) after the engraving/inlay work was completed.
When I first acquired this .38/44, I spent a lot of time trying to figure out who did the engraving. There is no doubt in my mind, (although I have not been able to verify to the extent it needs to be), that this engraving was done by Orville Kuhl, who did a lot of engraving for King Gunsight Company of San Francisco during the 30's. I have seen many other firearms that he has done, and are quite similar.
Smith & Wesson Forum - merlindrb's Album: Kuhl Engraved Guns
Roy Jinks told me that he could not verify the engraving ID.