1970 topps football printing mark?
 

has anyone seen anything like this? I don't really collect football but a friend found a bunch of pretty fresh 70' topps fb and this was in it.

From the edge of a sheet. Most sheets had them. I'm not sure when they started.
Here it's "slit A" next to the second card from the bottom on the right.

https://sports.ha.com/itm/football/1...-BidNow-071515

thx steve...I did a quick google search and found a similar but better example on amazon.