The term 'Rarely Seen Bills' refers to the two-dollar bill, which is a denomination of United States currency. The two-dollar bill is rarely seen in circulation due to its low demand and limited production. It is the least circulated of all U.S. paper currency, with only 1.2 billion bills in circulation as of 2019. Despite its rarity, the two-dollar bill is still legal tender and can be used for any purchase.