[swarmee]

Originally Posted by mintacular

What is flip stock ? Never heard that one

Flip stock is the term Topps invented recently as a parallel set to Topps Heritage, where they print the back of the card on the nice "white stock" and the front of the card on "gray stock" making it look like the sheets were fed into the printing presses upside down.
They super limited to like 5 of each card in most Heritage sets that have them.

https://www.comc.com/Cards,sh,i100,=flip+stock


2019 Topps Heritage High Number - [Base] - Flip Stock #501 - Michael Chavis
Courtesy of COMC.com


2019 Topps Heritage High Number - [Base] #501.1 - Michael Chavis (Batting Pose)
Courtesy of COMC.com

See if you can tell the difference just due to the images.

Edit: I believe there have been random vintage Topps cards found over the years that might have accidentally been printed this way, which inspired the parallel set.