Green’s Dictionary of Slang

two-thirty adj.

dirty.

1960		J. Franklyn Dict. of Rhy. Sl. 133/2: two-thirty Dirty. Late 19C., still used occasionally. It refers to grime, not to behaviour.
1979		R. Barker Fletcher’s Book of Rhy. Sl. 25: His bushel and peck was extremely two-thirty.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.