Extremely nice 19. Looks like the one I started my policing with, with the exception of the target hammer and trigger.
I wouldn't touch that finish,at least for years to come.
My finish was well worn on the 2 1/2 incher when I had it redone.

As to the coating question,I just sent the gun to Robar with instructions as to what I wanted done. The chambers are coated.The only places not covered with the NP3 is the rear sight and the bore.

I'm not aware of any additional surface prep charge. I believe the NP3 was applied over the original finish but I'm not 100% on that.