I would guess N frame because of the area behind the stock circle. No need to be real concerned with the chip. If it bothers you too much find a friendly dentist to fill it with the epoxy they use on teeth. I think the $250 guess is pretty low. I'd think $400 would be a reasonable amount to charge. Except ivory buyers are kind of finicky. They'll want to test fit them to a gun before paying.

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Dick Burg