Green’s Dictionary of Slang

(Aus./S.Afr. prison) in pl., handcuffs.

1901		W.A. Sun. Times (Perth) 4 Aug. 1/1: A well-known Groper potentate insisted on trying on a pair of American hand cuffs [...] having come in his dress suit, the owner of the ‘bangles’ had left the key at home.
1974		H. Levin Bandiet 184: I was in full prison uniform [...] plus hand-cuffs – ‘bangles’.