badge - an emblem (a small piece of plastic or cloth or metal) that signifies your status (rank or membership or affiliation etc.); "they checked everyone's badge before letting them in"

positive identification - evidence proving that you are who you say you are; evidence establishing that you are among the group of people already known to the system; recognition by the system leads to acceptance; "a system for positive identification can prevent the use of a single identity by several people"