Green’s Dictionary of Slang

brass n.2

also brass-nail, brass-nob
[rhy. sl.; brass nail = tail n. (5)]

1. a prostitute.

[UK]P. Allingham Cheapjack 203: The other words he used to describe them were ‘molls,’ ‘skirts,’ and ‘brassnails,’ although this last word is only used as a rule in reference to ladies of a certain definite profession.
[US]H. Corey Farewell, Mr Gangster! 279: Slang used by English criminals [...] Brass nob – a prostitute.
[UK]J. Curtis They Drive by Night 261: Queenie wasn’t such a bad-looking brass.
[UK]J. Maclaren-Ross ‘The Dark Diceman’ Bitten by the Tarantula (2005) 205: He thrust on [...] towards the brass nails on the batter.
[UK]P. Wildeblood Way of Life 34: The girl looked at him with a touch of hauteur. [...] ‘Stuck up brass, ain’t she?’ said the sailor.
[UK]B. Naughton ‘The Little Welsh Girl’ in Late Night on Watling Street (1969) 135: Course you could see she wasn’t a brassnob by the way she looked at you.
[UK]B. McGhee Cut and Run (1963) 55: She had tried them all. Starting as a shop-lifter and ‘brass-nail’ on the beat.
[UK]N. Dunn Up the Junction 37: What d’you think I am? Some high-class brass?
[UK]G.F. Newman Sir, You Bastard 43: A couple of brasses would have to be found later.
[Scot](con. mid-1960s) J. Patrick Glasgow Gang Observed 109: There [...] we could ‘chat up brass nails’.
[UK]T. Lewis GBH 62: A brass here [i.e. outside London] would be highly-polished in a different way, to express her occupation, not to conceal it.
[UK](con. 1900–30) A. Harding in Samuel East End Und. 281: Brass nail – Prostitute. The girls had the cheek of the devil.
[UK]Indep. on Sun. 11 Oct. 32: There is also a young lady [...] she is either Mrs Gruber or an upmarket brass.
[UK]N. ‘Razor’ Smith Raiders 23: [He] had a stream of top-class brasses tending to his nightly needs.
[UK]J.J. Connolly Viva La Madness 64: Sonny told me [...] to go and find myself a friendly sauna and punt for the deluxe polish off a creamy brass.

2. a woman; a wife or girlfriend.

[SA]Mail & Guardian (Johannesburg) 24 Sept. 🌐 But don’t tell the old brass. She’ll clip you round the earhole. The ladies don’t really like a toker.

In phrases

half-brass (n.)

a woman who associates with the prostitute milieu but is not a ‘working girl’ herself.

[UK]Partridge DSUE (8th edn) 522: [...] mid-C.20.
[UK]J. Morton Lowspeak.