lifter butt plate
 

A short while ago I picked up a 12 ga lifter from 1879 in not too rough shape.So far, Ive taken it apart and have tried to remove just the rust and congealed grease. When I got to the butt plate, there was no finish at all only a few places of rust. My question is: what was the butt plates original finish, nitre blue, case color or just polished metal?

Blued.

Thank you