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What Are Radar Notes?


Did you know that banknotes with certain types of serial numbers are highly collectible and can even be worth lots of money? There are all kinds of serial numbers that are worth collecting, and one of the most popular types of fancy serial number pieces to collect are called Radar Notes. Radar Notes have palindromic serial numbers – that means they read the same forward and backward. An example of this is a serial number that reads “02344320” or “24244242.”

This Series 1977 $100 Federal Reserve Note has a “radar” serial number reading “00099000.” Image is courtesy of Heritage Auctions, Click image to enlarge.

A palindrome is really just any kind of alphanumeric pattern that has the same order of characters when read in either direction. A popular palindrome phrase is, “A man a plan a canal Panama.” The “man,” as historians know, was United States President Theodore Roosevelt, the “plan” was a shorter maritime path between the Atlantic and Pacific Ocean basins, and the “canal”? That would be none other than the Panama Canal, a 50-mile artificial channel that was carved through the Central American nation of Panama and opened in 1914. And then there’s “Taco Cat.”

While some palindromes can convey a history lesson and others simply conjure up strange images of feline foodies, numismatic palindromes offer a world of possibilities for collectors. Numismatists love weird things on their money, and a Radar Note is quite unusual. Given the mathematic parameters within which Radar Notes exist, the chances of finding one among any given group of notes is about one in 10,000. This assumes that the note in question has eight numeric characters in the serial number ranging from “0” to “9” and also that the eight numerals are divided into two sets of four digits, with the second set a complete reverse arrangement of the first set.

Two interesting types of Radar Notes are ladder radars and repeater radars. A ladder radar features four consecutive digits counting up, one by one, such as “34566543.” Meanwhile, a repeater radar contains only two different digits that read in a palindromic binary fashion, such as “33555533.” A super radar note also carries just two different numbers, but the first and last digit are the same as each other and the middle six in the grouping are all the same numeral. An example of a super radar is “81111118.” The rules of math and probability say that a super radar will be found on only one note out of a random 1,111,111. Talk about a rare banknote!

While all Radar Notes are scarce, the rarest and most desirable tend to be the older notes. Values range depending upon the denomination and age of the banknote as well as its condition. Auction prices and market trends run the gamut from about $25 to $50 for a typical, basic Crisp Uncirculated $1 Radar Note of the contemporary period to more than $500 for a late 20th-century $100 Radar Note; prices can reach into the thousands of dollars for vintage bills with these peculiar numeric patterns, regardless of denomination.