It has been known that Ken Dryden, former NHL goaltender star from the 70’s is a VERY TOUGH Autograph to obtain, often refusing to sign any item he think’s will gain value from his signature.  One article shows this fact: https://windsorstar.com/news/in-progess-ken-dryden-hockey-jersey#:~:text=He%20just%20said%20no%20to,the%201972%20jersey%2C%20Dubs%20said.

“But when he approached Dryden after the ceremony to tell him the story behind his jersey and to have him autograph it, the former hockey player told him he wouldn’t autograph it because it would end up for auction on eBay one day, Dubs said.”

“Dryden made it clear when he agreed to the speaking engagement that he would autograph items but that he would personalize each autograph to prevent someone re-selling it too easily.”

If you collect hockey autographs, this one (especially on a Rookie Card) is RARE an not easily obtainable with only 5 graded PSA Topps Rookie cards and 9 graded O-Pee-Chee.