If you have a few $1 bills lying around, you could be sitting on hundreds of thousands of dollars.

Courtesy of the American Bureau of Engraving and Printing errortwo batches of $1 bills printed in November 2014 and July 2016 can now be worth as much as $150,000 a pop.

According to the personal finance site Rich nickel, the request for the first set was sent to a printing facility in Washington, DC in 2014, but the same request was somehow made in July 2016 and printed in Fort Worth, Texas. This resulted in invoices with duplicate serial numbers being circulated before the error was noticed.

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About six million pairs of banknotes are currently in circulation, although only nine pairs have been put back together to date.

According to USA Todaycoin collectors are willing to pay anywhere from $20,000 to $150,000 for a pair of faulty batches.

If you're the lucky owner of one of the bills, the “Series” date (which is next to the picture of George Washington) will say “2013 Series” with a Federal Reserve stamp “B” on top and a serial number ending in a “*” symbol. The range will fall between B00000001* – B00250000* or B03200001*-B09600000*.

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If you believe you have one (or a pair) of receipts, you can submit it to an online database called Project 2013bwho tries to catalog all the misprinted bills and eventually merge them all together.

To date, over 36,000 invoices have been catalogued.