A radar bill refers to a paper currency bill with a special type of serial number known as a "radar serial number." This serial number reads the same forwards and backwards, like the word "radar" itself—a palindrome. For example, a serial number like 14233241 or 11022011 is considered a radar serial number. There are special types of radar serial numbers including:
- Super radars: The same first and last digit with six of the same digit in between (e.g., 84444448).
- Radar repeaters: Serial numbers where the first four digits match the last four digits (e.g., 25522552).
Radar bills are collectible because these special serial numbers are rare. In a print run of about 96 million notes, approximately 9,600 radar serial number bills are produced, meaning about 1 in every 10,000 bills may have a radar number. Value-wise, radar serial number bills in circulated condition are usually worth close to their face value, but uncirculated bills with radar serial numbers can sell for premiums. Typical values are around $10 to $50 for $1 radar bills, with rare types such as super radars or certain variations fetching over $100 in uncirculated condition. In essence, a radar bill is a collectible currency note distinguished by a palindrome serial number that can make it more valuable than regular bills, especially if the bill is in pristine condition.
