Late to the party, as always . . . . . but . . . .
This is Color Case Hardening . . . . . slide is blued over color case / case color hardened frame.
Nitre Blued small parts on a blued gun . . . .
And then, what is marketed as Carbona Blue, Carbona Black, or sometimes Carbonia . . . .
Carbona Blue/Black finish by Turnbull . . . .
This is Color Case Hardening . . . . . slide is blued over color case / case color hardened frame.
Nitre Blued small parts on a blued gun . . . .
And then, what is marketed as Carbona Blue, Carbona Black, or sometimes Carbonia . . . .
Carbona Blue/Black finish by Turnbull . . . .