How much is a 1934 series 50.00 bill worth with green seal on back?

Face value to $70 depending on condition.

BTW, the seal should be on the bill's front. If it's on the same side as the picture of the U.S. Capitol, then you have a printing error that could be worth several times its face value, but you'd need to have it appraised in person by someone who specializes in error currency.