PxT
Do not try to lick it off (trust me)
So this is sort of clever in a why-didn't-I-think-of-that way.

iTunes gift cards, and most gift cards really, used to have a problem in that if you scratched off the silver covering that protects the redemption code from being snooped, there was a chance you could scratch too hard and take the code itself off as well.  In time, the powers that be started admonishing you to scratch "gently" to try and solve that problem.  From experience though I can say that even if you took care it was still possible to inadvertently scratch off part of the code -- sometimes that silver gunk just doesn't want to come off. 

Lo and behold, the problem seems to have been solved at last.  There is now a clear plastic barrier over the code and then the silver scratchable coating sits on top of that so that you can either scrape it off – and unless you scrape hard enough to break through the plastic barrier you can't damage the code – or simply peel the whole thing back.  Genius?  Probably not, but it solves a common problem in an elegant way.  I wish I would have thought of it, I bet that this is patented by someone!