Green’s Dictionary of Slang

(usu. Aus.) second-rate; fake, counterfeit, of inferior make.

1825		Pierce Egan’s Life in London 24 Apr. 101/1: ‘Walker!’ replied Josh, ‘I suppose your blunt is in the Brum line, all counterfeits!’.
1881		Standard 27 Sept. 2/1: The Lobster Smack, the house of call for the ‘brum’ – i.e. unlicensed – pilots, who are patronised by captains objecting to the higher dues charged by the regular Trinity House men at Gravesend.
1902		Bulletin (Sydney) 26 Jul. 12/3: Senator Matheson, a wise man out of the West, is hotly opposed to the 25 per cent. duty on ‘brum.’ jewellery, and in the House drew a pathetic picture of the poor woman robbed of her little adornments by a shameful tyranny. [Ibid.] 9 Aug. 8/4: [Y]et the time must surely come / When it isn’t safe to tell them that the diadem is ‘brum.’.
1910		Bulletin (Sydney) 24 Nov. 24/1: The two destroyers which were built in England haven’t arrived yet. So the question whether they are also ‘brum’ is unsettled.
1953		K. Tennant Joyful Condemned 328: You don’t have to appear in that little brum court they have at the Reception House.
1966		P. White Solid Mandala (1976) 227: A brum two-bob.