A 2020 FUN Show attendee discovered the note in her change at the show.

A woman who made a purchase at the January 2020 Florida United Numismatists (FUN) Show in Orlando got an unexpected bonus in her change: a $20 bill with a valuable error. She immediately submitted the note to Paper Money Guaranty® (PMG®), which confirmed that the 2013 $20 Federal Reserve Note (Boston) had an authentic — and quite rare — mismatched serial number error.

A PMG-certified modern US note with this error is likely worth hundreds of dollars or more, resulting in a tidy profit for the woman who discovered it in her change. For instance, another 2013 $20 Federal Reserve Note — a Richmond example graded PMG 66 Gem Uncirculated EPQ — with a mismatched serial number error sold for $1,140 at a Heritage Auctions sale at the January 2020 FUN Show. Meanwhile, in the same sale, a 1977A $5 Federal Reserve Note (St. Louis) with the same error graded PMG 40 Extremely Fine EPQ realized $750.

"It was such a thrill to find a rare banknote in change right at the FUN Show," said Tammy Demars, a Texas resident who helps manage a Facebook group called Coins & Currency Live Auctions. "After I realized I had a potentially valuable note, I brought it directly to the PMG booth for confirmation."

Paper money collectors place a premium on these notes because quality control measures at the US Bureau of Engraving and Printing usually keep such errors from ever reaching circulation. Banknotes' serial numbers are vital in helping to ensure the integrity of paper money.

The serial numbers on the note (MA54550151B and MA54545151B) differ in their middle two digits: 45 vs. 50. The serial numbers printed on a note are imparted by a pair of numbering wheels. When the serial numbers don't match, it indicates something went wrong — such as one of the numbering wheels was temporarily stuck.

"This note is an excellent reminder that great numismatic discoveries can still be made simply by looking at our pocket change," said Mark Salzberg, Chairman of PMG. "The condition of this note suggests that quite a few people unwittingly let a valuable rarity slip through their fingers."

Collectors and dealers who have error notes can submit them to PMG for certification under the Economy Special grading tier or higher with the error noted under the Variety/Pedigree column.