I don't think it's American at all.
Maybe whoever owns it now can actually test the wood, but that does not look like maple to me. George, unfortunately, as nice a guy as he was, believed a lot of things he was told by owners without question.
I think this is simply another heavily-used European rifle that may have a somewhat long American history but was not made here. And there are a lot of them.
The Cooper engraving is just silly and probably dates to the late 19th or early 20th century.