Buttplate color

[Kensal Rise]

What you are dealing with is most probably a material called Bakelite, a very early form of plastic/resin. This from Wikipedia:

"It is a thermosetting phenol formaldehyde resin, formed from an elimination reaction of phenol with formaldehyde."

This is the stuff that turns brown when you expose it to the wrong solvents or heat. I'm guessing because of the formaldehyde element. You can stain it black, but it's still brown underneath.

[Bill Murphy]

I have a couple of Lefevers with brown buttplates, Parkers also. I would rather leave them as is than mess with them. Some have been boiled to make them that way, some came to me that way. I like them, no matter how they got that way.

[Autumn Daze]

John, Parker Bros. butt plates are made from "Gutta Percha" a form of rubber at least into the Remington era. The Parker marked plate's made by Remington may be bakelite.