ridjrnr -
I have a Tennessee-made longrifle with a front sight that is partly copper. The base is copper; the blade is coin silver or another silver colored metal. The rear sight is all iron. For some reason, I have always believed that this type front sight was not uncommon, although I would be hard-pressed to prove it. The blade is not very tall, probably 3/32" above the top barrel flat; almost invisible when shooting.
This rifle has been my family since the 1830's.
Bill Brockway