I have a US currency dollar bill which is a 50 dollar bill on the fron and a 5 dollar bill on the back.?

Question

AND ITS REAL I TOOK IT TO THE BANK AND THEY PUT IT THROUGH THEIR MACHINES AND IT PASSED!!!

AND ITS REAL I TOOK IT TO THE BANK AND THEY PUT IT THROUGH THEIR MACHINES AND IT PASSED!!! HOW MUCH IS IT WORTH? ANY IDEA?

Answer 1

I would send it to one of the major grading services, since this would also serve as a guarantee that the note is authentic when you sell. Assuming that it is found to be genuine, such an error would be worth several hundred dollars, at a minimum. It costs money to have it graded, but you will get far more back when you sell. The link below is for one of the major grading services.
I will have to admit that I am somewhat skeptical, Please do the following (and this only applies to Series 1996 and later US banknotes):
Hold the note up to the light. Is the watermark Lincoln or Grant? Also, look at the mylar thread embedded in the paper. There is lettering on the mylar thread - what does it say?
There is a possibility that one side of the note had the design bleached off and then the higher denomination was applied with a color copier.
I wish you luck.

Answer 2

ask the bank