I have told this one before, but perhaps worth repeating in this thread.
I live in Sydney, (down under).
I was in a coin shop, and found a nice looking SLQ in a junk bin. Looked about EF35 or thereabouts.
In the grading system used for World coins, that equates to around good VF
I bought it for a dollar.
I WAS NOT a specialist in U.S. coins, and neither was the dealer. MY principal interest at the time was ancient coins, and still is.
I checked it out about a month later: Guess what?
A '23s!
It was later auctioned for $330. That was about 20 years ago.
I look back on this story with some regret, because I have since developed quite an interest in U.S. coins and now have over 200 of them.