Here's a card with a different type of cylinder transfer where a foreign
object got stuck in the impression cylinder and created an odd mark on
the front and an indentation on the back.
Willett Front 800 dpi.jpg
Willett - Copy.jpg
Steve B explains it in this thread and there's a link in that thread where Chris B
was the first to discover that it was a reoccurring print flaw
https://www.net54baseball.com/showthread.php?t=198822