I'm a relatively infrequent poster here, but I wanted to share this research I've been doing on the 1980 Topps Henderson rookie card. I have been struck that PSA has only given out 24 Gem Mint 10 grades out of almost 21,000 cards submitted. That seemed very unusual, so I set out to test (as scientifically as possible) the explanations that collectors are frequently given.
It's a long video with a lot of analytical data, but I felt it was justified given the stature of this card in our Hobby.
https://youtu.be/6wTMS1dmddc
I hope you enjoy it.