MIB is a way of indicating that a dispenser is in its orgiginal packaging consisting of a polythene ("poly") bag.
MIB is an acronym for Mint In Bag. It is a way of not only indicating the type of packaging in which the dispenser can be found (in a bag), but also the condition of the dispenser (mint).
Most bagged Pez include two packs of candy and one of the various paper inserts, as well as the Pez dispenser.
Different countries or geographic zones have different bag designs.
The color of the bag can also vary through the years.