What is difference between a red seal two dollar bill and one without?

Answer 1

Most bills with red seals are an older form of currency called U.S. Notes. U.S. Notes were essentially a parallel form of currency to Federal Reserve Notes, except they were issued directly by the government without involving the Fed. $2 and $5 were the most common U.S. notes, but there were also some $10 and $100 bills issued too.

In the mid-1960s the government decided there was no purpose in having two parallel currency systems because they were entirely interchangeable. The Federal Reserve system was given sole authority over currency distribution and production of U.S. Notes ended around 1967. All currency printed after that time has been in the form of Federal Reserve Notes which carry a green seal.

As far as value is concerned, $2 Fed notes are only worth face value if received in change. $2 U.S. notes are worth a small premium (50c or $1) to collectors, mostly because they're older and less common, but are otherwise entirely equivalent to their green counterparts.