In American Firearms Makers by A. Merwyn Carey, there is the following entry...
Levi Coon, Sr, 1776-1821. Shop located at Ithaca, NY, made flintlock Kentucky rifles, business carried on by sons, Levi, Jr. and Daniel, into percussion period.
I would think 1780 is too early for a "Plains" rifle, but Daniel could be your man.
-Ron