The only coin I ever paid over $100 in a 2x2 like that was an Italian States (Milan) 1794 Thaler. It's a big one with a diameter of 42mm and looked around VF25 ish. Happily paid $125 for it, should have kept it as I love world coins as well as American. Think it still has the same book value now so I could get another I guess.
I'm thinking "HRSBY" is a price code, that tells the owner how much he paid. If you could decode it, you'd have bargaining power. A shop (not coins) I worked at used PATHFINDER, a word with 10 unique letters, each one represents 0-9, so when a customer wanted to dicker, you knew how much you paid. Very old school.