One Dollar Bill.
It has the oldest design of any bill in circulation. The $1 bill has—by far—the worst return on investment of any bill you can counterfeit, so it’s not a huge problem for the Federal Reserve and Bureau of Engraving. No new countermeasures mean its design hasn’t really needed to change since 1963.
YOU MIGHT ALSO LIKE Twenty Dollar Bills ($20)
200 ($1)Bills, 500 ($1)Bills, 1000 ($1)Bills, 5000 ($1)Bills, 10000 ($1)Bills