Collectors are willing to pay a small fortune for 'radar' bills that could be hiding in your wallet.
A 'radar' bill is a note with a palindrome serial number, a series of numbers that reads the same forward and backward.
An example of a palindrome would be 12344321, but several conditions and patterns determine the value collectors are willing to pay.
Typically, $1 'radar' bills go for anywhere between $10 and $50 and can feature multiple patterns such as quad center, radars, and super radars.
A super radar has only two different numbers, with the first and last digits identical and the middle six all the same numeral. An example would read as 32222223.
The probability of having a super radar bill is one out of 1,111,111 notes, according to PCGS.
Heritage Auctions have seen bills with palindromic serial numbers sell for much higher than $1,000, according to KTLA.
Those rare serial bills were listed on eBay between $10 and $400 at the time of this report.
A 'radar' bill is a note with a palindrome serial number, a series of numbers that reads the same forward and backward. The serial number can be seen below the G on the left side of the bill. This particular radar bills number is 57000075
Larger notes such as the $20 bill pictured are at times more valuable because they are generally 'produced in smaller numbers and thus unusual number sequences are relatively less common,' said Doug Mudd, the curator and director of the American Numismatic Association's Edward C. Rochette Money Museum, to KTLA
Radar bills aren't limited to the $1 note, as all denominations of bills can feature these rare patterns.
Some of the most expensive bills featuring the sought-after serial sequences are larger notes, said Doug Mudd, the curator and director of the American Numismatic Association's Edward C. Rochette Money Museum, to KTLA.
Mudd explained that larger bills are more valuable because they are generally 'produced in smaller numbers and thus unusual number sequences are relatively less common.'
But Mudd added that radar bills often go unnoticed because most people are not looking for them.
'Again, [it's] another niche collecting area,' Mudd told the outlet, 'but with greater significant value to the right audience.'
Collectors and numerologists are not only interested in radar bills, but also serial numbers that are simply out of the ordinary, such as 10000000 or 12345678.
Heritage Auctions have seen bills with palindromic serial numbers sell for much higher than $1,000 but if your wallet is empty of any cash check your piggy bank for a rare quarter from 1970 that could be worth $35,000
Perhaps your wallet is free of any of the palindromic bills, it could be time to crack open the piggy bank to check if you have a rare quarter from 1970 that could be worth $35,000.
To find out if you have one, you'll need to look very carefully, probably with a magnifying glass, to spot a faint trace of the year '1941', upside-down just above the world 'dollar'.
However, the chances of actually owning one are highly unlikely as proof coins such as these are not intended for circulation.
But if you're after something slightly less pricey, similar 1970 quarters are being sold for $2,500 and for $5,000, also on eBay.