Ever wondered how the iTunes cards works when you scan the code with your phone? You'll see a overlay of the code on your screen when you scan it, but how?
The company Equinux found out that Apple is using an invisible font for the code. They have found clues in the 'CoreRecognition.framework' about a font called Scancardium. This is the font Apple is using for the cards, also the scanning code looks for the exact retangle size around the code when it's scanning.
With this information that Equinux found, it's possible for other developers to create their own App Store cards. The only thing the developers needs to do is to generate their own codes via iTunes Connect.
You can test it out on your Mac, you can find the font in: /System/Library/PrivateFrameworks/
CoreRecognition.framework/Resources/Fonts/