The phrase "badge number" refers to a unique identification code assigned to people who hold certain positions such as police officers or security guards. It helps identify and differentiate them from others in their profession. Full definition
With anyone you contact about this theft, be sure to take notes of the names, dates, times, phone numbers and badge numbers of people you've talked to. (rismedia.com)
One cop (Takeshi Kaneshiro)- both are identified only by badge number - finds himself attracted to a beautiful woman (Brigitte Lin) in a bar, not realizing she's a dope dealer who's handy with a gun. (sfgate.com)