At its heart the cryptographic technique called chaffing entails concealing a message within a larger whole, like grain amid chaff. In simplified form it can be applied to New York's health code, too. Here the message is the restaurant's letter grade, which is required to be affixed to the front of the shop, and the chaff (which I believe is coincidental rather than intentional) includes the permanent signage and miscellaneous papers on the door and windows. The letter grade is plain to read, but only with concerted attention.
Sunset Park, Brooklyn