There are several numbers and sets of numbers and letters on a dollar bill.
The Note Number Position shows the position on the printing plate that the bill occupied.
The Federal Reserve District Number indicates which of the twelve Federal Reserve Districts printed the bill. It appears just inside each corner of the bill, next to the denomination.
The letter inside the Federal Reserve Seal also shows where the bill was printed. This Letter is also the prefix for the Serial Number.
The Serial Number is a unique number assigned to each bill. It consists of the Federal Reserve District Number, a serial number, and a letter suffix, which shows which print run the bill was made under.
The Series Date shows the series the bill was issued during. This number only changes if there is a design change, a new Secretary of the Treasury, or a new Treasurer of the Unites States (if the last, the letter "A" is appended to the year).
The Plate Serial Number shows which plate the bill was printed from.
answered Jul 17 '11 at 14:37