Note that the series designation has been used for notes of two different design generations, and that it is paired with a different serial prefix letter in each case. The recently redesigned Federal Reserve Notes, beginning with Serieshave two letters rather than one at the beginning of the serial number. The eight digits can be anything from tobut in recent years the highest serial numbers have been reserved for the BEP's souvenir uncut sheets of currency, and therefore not issued for circulation. The star indicates that the note is a replacement for another note that was found to be defective or damaged during printing see the section on star notes below. On some notes, a star appears in place of the last letter. The letter O is not used because of its similarity to the digit 0, and the letter Z is not used because it is reserved for specimen notes or test printings.

The last letter has no particular meaning it merely advances through the alphabet as each block of notes is printed. The first letter of such a serial number identifies the Federal Reserve Bank which issued the note since there are twelve FRBs, this letter is always between A and L.

Federal reserve serial number lookup