Posted By:
Julie1) you follow it's provenance and
2) you check with the bat and glove makers to see if the type in question was period.
I guess that's about all you can do, and I guess it can be done with some, but not with others...
The big problem is, respected authenticators are missing the boat, and not doing these two things--leaving it to someone else, later, to do them, and discover their goofs.