Green’s Dictionary of Slang

1. a sovereign, a 20-shilling coin.

1732		Harlot’s Progress 14: With his left hand he tip’d a Broad-piece.
1984		Partridge DSUE (8th edn) 137/2: C.17–19.

2. usu. in pl., money.

1923		J. Manchon Le Slang.
1965		K. Marlowe Mr Madam (1967) 146: The guys [pimps] came in and got their ‘broads’ with their palms outstretched. Each girl opened her purse and pulled out a wad of money to turn over to her pimp.

3. any form of documentation, e.g. identification papers, rations book, driving licence.

1977

D. Powis Signs of Crime 175: Broads [...] identity documents.

4. a credit or similar card.

1977		D. Powis Signs of Crime 175: Broads [...] recently, credit cards.
1989		J. Morton Lowspeak 31: Broad [...] 3. a credit card.

5. see broads n. (1) and combs. for all refs. to playing cards.