Well, CMD, sounds like you have this piece pretty well figured out.
It's obviously clay because of the fingerprints, and you found it in an area
where you might find NA artifacts, but it's still a good question whether it is
NA or not.
I have never seen a NA bead like that before. Most types would be smoothed and
have the ridges and fingerprints smoothed out. So that does make you wonder about
the Girl Scout project from the 40's. If you could find even one other example of
a bead like that from aboriginal context then I would say mystery solved.
The only thing I can think of that might help decide it one way or the other is to
look closely at the shell. It kind of looks like that shell/sand has gotten stuck to the
outside of the piece incidentally. If it a true shell tempered clay then the shell
will be mixed throughout the clay, and that would be a definite sign of Native
American manufacture.
Might be hard to tell for sure without whacking it with a hammer.
JoeM