Green’s Dictionary of Slang

threepen’orth n.

(UK Und.) a three year prison sentence.

1938

F.D. Sharpe Sharpe of the Flying Squad 333: threepen’orth : Three years’ penal servitude.

In compounds

three-pennorth of God-help-us (n.)

(Aus.) a derisive description.

1924

Dly Teleg. (Launceston) 17 July 6/5: We know it must be cold when we see young people going about with a hump on them and a general look of three-pennorth of God-help-us badly tied up.