Green’s Dictionary of Slang

1. of a detective, to show one's badge to prove one’s authority, usu. prior to an arrest .

1970		J. Wambaugh New Centurions 225: ‘She thought he was a PO-lice impersonator when he finally badged her’.
2012		G. Pelecanos (con. 1972) What It Was 99: The transaction had been made and [...] his girl had been badged.
2016		D. Whish-Wilson Old Scores [ebook] It was the third man who badged Swann [...] ‘Major Crimes. We’d like you to accompany us to Central. A little chat. Purely voluntary at this point’.

2. (US) to show one’s badge (typically that of a police department) to gain (free) admission.

1971		E.E. Landy Underground Dict. (1972).
1975		J. Wambaugh Choirboys (1976) 263: You get a broad in the car [...] badge her and bring her back here quick.
1997		J. Birmingham Tasmanian Babes Fiasco (1998) 211: They badged me. ‘Detectives Eady and Belcher,’ said the taller one.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 21: You badged in. The owner loved cops. Your host — Jack Ruby.
2021		J. Ellroy Widespread Panic 78: Harry badged our waiter. He slipped us a jug at [...] half-price.