Skeleton Steel Butt Plate Finish?

[Jim Kremmel]

My apologies if this has been discussed, but I’ve not been able to determine how the skeleton steel butt plates were originally finished. Were they case hardened, or nitre blued? Something else? If it matters, I’m particularly interested in a D grade circa 1900 gun. Thanks. Jim

[David C Porter]

charcoal bluing - Turnbull Restorations does this type of bluing

[Brian Dudley]

Nitre blue. Same as the trigger guards.

[Bill Murphy]

Yup. Thanks Brian.