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But if you look closely it had a robot at each end so not a brush. More pictures from other angles might help.

Either punched or burned in. If back to 1800's it could be whale bone. Might be a neat artifact.

Are they thin or thick? Does the one pin and washer look like others you have seen?
If thick and not the normal pin they may have been made by the owner and decorated by him. It's hard to tell from...