If you have or can find a complete checklist of them, I say go for it. I don't think anyone would complain as long as there is a complete CL. A postcard is still a trading card b/c there is interest in owning them and trading for them.
If complete CL's could be made, there would be a ton more sets in the Racing section for all of the "Hero Cards" made every year. They are usually postcard-sized (3x5 or 4x6), but there is no way to know how many drivers have them for any given year or how many versions for any driver.
NO PWE's EVER!!! PLZ PM me 1st before sending any offer. ONLY selling cards as of March 2024. No trades or purchases right now.
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Largest total PC card collections by Team, then Athlete (as of 3/22/24):
STL Cardinals (MLB) - 8810; Carolina Panthers - 2888; GB Packers - 1790+ cards
Mark Martin (NASCAR) - 2038 cards; Jimmie Johnson (NASCAR) - 1875 cards; Jeff Gordon (NASCAR) - 1594; Ricky Rudd (NASCAR) - 839; Ozzie Smith (MLB) - 707