Green’s Dictionary of Slang

1. (US) $1.00.

1919

A. Baer Two and Three 8 Feb. [synd. col.] Dempsey [...] training for that twenty-seven thousand certificates.

2. (N.Z. prison) a criminal carge or conviction.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 39/2: certificate n. a criminal charge or conviction.