I know that this is the postwar forum, but you asked for the most overrated card of all time. It's the T206 Magie error card. It's consider an icon, but all it really is is a 1909 version of a typo.
A PSA 1 sold last night for $5,800. What does a 1952 Mantle in PSA 1 sell for? (I'm really asking, I don't know postwar cards). A Magie shouldn't even be anywhere near as valuable as a '52 Mantle, but I'll bet it's close. If it wasn't part of the T206 set, it would be largely forgotten instead of being a "classic."
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