For some reason, Carl Yastrzemski autographs are rarely discussed on this site.  During his playing days, he was a very tough signer, but that is being masked by the thousands of items he has signed at shows since his retirement.

Every once in a while, I see an obvious forgery that has been authenticated by one of the top TPA's.  Here are two that are currently listed on ebay:

these are 100% forgeries.  If anyone looks at the hundreds of Yaz signatures on ebay at any point in time, you will see a consistency that looks nothing like these pictured.

I have been studying and collecting Yaz autographs for over 30 years, and I never seen either one of these styles.