This is a very good effect.  And even better -- it is a very good method, well-thought-out, not really difficult to do, and easy to reset.   

The effect looks like this:  You show a few one dollar bills, and then you notice that one has the "seals" printed backwards -- that is, the gray seal is where the green seal should be, and vice versa.   "That's usually the sign of a counterfeit bill!  but I can fix it."    You run your finger over the gray seal and it turns green, and you continue to run your finger over the other seal which is now gray.    The bill can now be compared to the other bills to show the seals are properly oriented.   

Oh yeah, the changed bill is immediately handed for examination.  Or even spent -- it is ungimmicked.

Best online price I found today for this DVD was about $25. 

Opened for inspection, but in new, unused condition, with DVD instructions. 

(also includes the secret gimmicks for you to use in constructing the effect.)