Green’s Dictionary of Slang

(US police) the officer’s gun.

1983		Neaman & Silver Euphemisms 169: The most efficacious of these [i.e. the policeman’s weapons] is still the gun, also known as a Crowd Pleaser (U.S., 1970s).
2000		(con. 1940s–60s) Décharné Straight from the Fridge Dad 39: Crowd pleaser Police gun.