potsy, n. — Green’s Dictionary of Slang

potsy n.

[the tin (used for pots) that is allegedly made into badges; also note potsy, a flat stone used for the game of potsy (UK: hopscotch)]

(US) a police badge, an identification card.

1932		Sun (N.Y.) 26 Mar. 18/3: I recently bought a Sun which gave a vocabulary of firemen’s slang, in which ‘potsy’ was the word for ‘badge’. I have also found policemen and detectives who referred to their badges in this manner .
1946		N.Y. Times 15 Dec. SM16: Tin: any badge of office, also potsy.
1952		(con. 1920s) ‘Harry Grey’ Hoods (1953) 247: ‘Cockeye, get that box of “potsies” out of the closet.’ [...] He scattered an assortment of shiny badges on the table.
1958		M. Berger in N.Y. Times 20 Oct. 34/1: A detective’s shield is a button, potsy, or tin.
1979		K. Bonfiglioli After You with the Pistol (1991) 332: ‘Flash the tin,’ I said in my Bogart voice [...] ‘Let’s see the potsy.’.