If you look in your wallet right now, chances are you’d find at least one $1 bill. You probably don’t think much about your $1 bills. After all, it’s not like $1 can even get you anything these days. However, you might want to take a closer look at the $1 bills you have lying around — if they have a certain serial number stamped on them, they could be worth a lot more than a single dollar.

A website called CoolSerialNumbers.com is currently collecting currency with “fancy” serial numbers. If you have a bill with one of these fancy serial numbers on it, you could stand to make hundreds or even thousands of dollars by selling the site your bill. Here’s what to look for:

7 repeating digits in a row on $1 Federal Reserve notes (e.g., 09999999, 18888888, 19999999, etc.)

7 of a kind on $1 Federal Reserve notes (e.g., 00010000, 00090000, 90999999, etc.)
Super radars on $1 Federal Reserve Notes (e,g,, 01111110, 10000001, 80000008, etc.)
Super repeaters on $1 Federal Reserve notes (e.g., 67676767)

Double quads on $1 Federal Reserve notes (e.g., 11110000, 44440000, 88880000, etc.)