Green’s Dictionary of Slang

1. (also the iron, the ironing) a toss (note Cockney pron. torss).

1932		‘P.P.’ Rhy. Sl.
1938		F.D. Sharpe Sharpe of the Flying Squad 278: Crooks are sometimes described by the fraternity as being ‘at the iron.’ This term is derived from the slang description of the Toss – ‘The Iron Horse.’ An Underworld man offering to toss for drinks will often say: ‘I’ll iron you for it’. [Ibid.] 331: iron horse: The toss (tossing with coins). Sometimes abbreviated to ‘the Iron,’ or ‘Ironing.’ (I’ll iron you for it’ – ‘I’ll toss you for it.’).
1960		J. Franklyn Dict. of Rhy. Sl.
1969		S.T. Kendall Up the Frog.
1992		R. Puxley Cockney Rabbit.

2. a racecourse.

1960		J. Franklyn Dict. of Rhy. Sl.
1992		R. Puxley Cockney Rabbit.