Any chance that you have access to the original box which would have a product code on the label?
The gold fill was done after it left the factory.
The wood grips are probably not original either. . . . . I also changed mine to wood grips
Is what you have a Mountain Gun?
A Mountain gun is 4" tapered barrel, Round Butt frame, Black ramp and black notch rear sight, black powder bevel on front of cylinder. It would have shipped with rubber grips
Finally got to talk to shop owner about it, he said the finish is factory but is so "deep it looks black; he hasn't seen another gun that black looking, someone mentioned the inlay kit and that is his opinion also. This owner is now deceased and the estate has brought in 87 handguns for consignment, he knew the owner and said "he was a bit of a "Tinkerer"....It's priced at new gun price's, such is life in California for a gun owner....
The gold inlay neither adds or subtracts from the value. The 57-6 variation was introduced in 2009, so if its in immaculate condition its worth paying today's price. All I can suggest is go see it.
It is pristine condition and the six inch version, i just whittled my pistol calibers down and don't know if want to add another..LOL...If any SoCal brothers are interested shoot me a PM....