Green’s Dictionary of Slang

1. (Aus.) £1; thus half jim, ten shillings.

1900		Bulletin (Sydney) 2 June 14/2: And I hadn’t more’n two Jim in my kick. No more fixed deposits for me.
1901		W.A. Sun. Times (Perth) 22 Dec. 1/1: Having paid a large cheque by messenger [he] returned with 10s. too much change [...] the corpulent strategist calmly divided the half ‘Jim’ with the Mercury.
1903		Sun. Times (Perth) 8 Mar. 1/1: The jim-a-week juggins handed the flower over.
1904		Sun. Times (Perth) 2 Oct. 1/1: Missing a sovereign he incontinently fired her [.e.a barmaid] [but] not knowing of the contretemps his own son boasted of having pinched the jim.
1904		Sun. Times (Perth) 31 Jan. 1/1: As the unclean Chow had bunged in his half-jim he refused to flit.
1906		E. Dyson Fact’ry ’Ands 214: Acourse I parted me arf jim — couldn’t have ther brick face t’ do less under ther circs. [Ibid.] 219: ’E’s bin givin’ Magill guff erbout marriage [...] ’n’ ther spiel was good fer fifteen jim, ther savin’s iv er lifetime.
1910		Bulletin (Sydney) 15 Dec. 25/3: Yes, he has enough for his fare – has ‘half a jim’ concealed in secret places.
1914		E. Dyson Spats’ Fact’ry (1922) 66: Here’s him, a lay member iv the Carter’s Union, not drawin’ a touch over four jims ev’ry second Friday.
1926		E.G. Murphy ‘Snores’ Dryblower’s Verses 93: As if a bloke ’ad just got wise ’e’d lorst an ’arf a jim.

2. money.

1931

‘William Hatfield’ Sheepmates 21: ‘You book it well ahead and put in the solid Jim.’ (What? — Thirteen and ninepence, and I have to pay two and nine to see?).