It is a piece of paper measuring 2 5/8" by 6 1/8" with a thickness of .0043". The composition of the paper and ink is a state secret. New notes will stack 233 to an inch, if not compressed, and 490 notes weigh a lb. Over 2 billion bills are in circulation, each with an average life span of 18 months.

U.S. Currency, as we know it today, is a Federal Reserve note. It is issued by the 12 Federal Reserve banks scattered across the U.S. under the auspices of the national Government which prints the bills.

On your dollar bill, there are serial numbers with two letter and eight numbers. The first letter (which will be between A and L) indicates which bank issued the bill. The letters stand for:

• A = Boston
• B = New York
• C = Philadelphia
• D = Cleveland
• E = Richmond
• F = Atlanta
• G = Chicago
• H = St. Louis
• I = Minneapolis
• K = Dallas
• L = San Francisco

As it is the most used in international transactions, the U.S. dollar is the world's primary reserve currency. Several countries use it as their official currency, and in many others it is the de facto currency.

The Bureau takes measures to prevent counterfeiting, which includes enhancing the currency design every 7 to 10 years. There are also a variety of other precautions that have been taken over the years.