Don't forget about the 1991 Topps MLB dark-logo back vs. the base set (which appears to be the "glow-in-the-dark" set, but actually only glows in a blacklight).
I had also never heard of the 1990 Topps NFL disclaimer cards, any UD hologram variations, or the '91 Topps back variations until I joined this site and started adding my cards to my collection here.
I'm not a set collector, so none of that messes up sets for me, but I am a player collector and those variants added more cunfusion to my haves and wants for certain players in both sports.
As for coins, Billy is right that "D" is for Denver, and of course "P" is for Philly. But don't forget about "S" for San Francisco for certain years. My coin collection isn't about age or value. It's purely a collection of interesting coins. Most of mine are the US coins that aren't common in your change from the store, but I also have coins from many countries around the world. Some of my biggest collections ARE very common though. I hand-collected the 50-states quarter set and am STILL missing one coin to complete the US Territories collection. I've been working on the US Parks Quarters since they started, but they are much harder to get than the state quarters were. I WAS working on the Gold Dollar US Presidents set, but those coins are nearly impossible to find in change now! My coins don't include anything before 1901, except replicas. I THINK I have at least one example of every Canadian coin for the past 50+ years, but one of our Canadian members would have to confirm that for me. I also have coins from Mexico, Belize, Japan, China, Hungary and some other countries that escape my mind right now. I'm not sure if I have a coin from South America, Africa or Australia to complete the world tour of coins. I haven't looked at the total collection in quite a while now. My coin-goal for the past several years was to find the missing US Territories coin (incomplete) and keep getting the US Parks coins (still gaining).
I'm not even going to get into the Pinnacle-brand sports coins that I have or need!
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