Dan Marino Rookie Card question

Hey folks, I have a Marino rookie card that looks just like this one on ebay. My question is... what's up with the weird white smudgy circle symbol in the black area. My card has this same symbol and I've always wondered what it is. Searching around ebay, I've seen this same symbol on several Marino rookie cards (maybe... 5%? not a lot of them, but enough that it's a thing). Anyone have any idea what this is about?

A little more context... I bought this at a card show around 1990 as a kid. I've owned it that whole time.