Green’s Dictionary of Slang

rock of ages n.²

wages.

1943		R. Llewellyn None But the Lonely Heart 21: The blokes as work there got to draw their rock of ages to get the roast and boiled of a Sunday.
1960		J. Franklyn Dict. Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1981		P. Wright Cockney Dialect and Sl. 104: rock of ages ‘wages’.
1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.
2013		T. Peacock More You Bet 83: The wages, or in rhyming slang, the ‘rock of ages’, were paid at the end of each working day, in cash.