Green’s Dictionary of Slang

(Aus. Und.) of the police, an attempt to extort a bribe.

1993

Smith & Noble Neddy (1998) 239: It was going to cost me another $5000 to ensure that the two statements made by the eyewitnesses would vanish. I thought this was a cold stamp [a deceitful attempt to extort money] and I told [the policeman] so.