Green’s Dictionary of Slang

(Aus./N.Z.) a shilling.

1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 107: OGG: slang a shilling.
1937		J. Curtis You’re in the Racket, Too 211: ‘That’ll be eleven shillings, please.’ Eleven og. What a berk.
1953		J. Franklyn Cockney 290: The word ogg is rarely if ever used to describe a shilling, but is frequently called into service for a multiplicity of shillings – ‘thirty ogg’, ‘fifty ogg’.
1980		(con. 1930s) Barltrop & Wolveridge Muvver Tongue 17: A shilling : a bob, a deaner, an ogg.