Green’s Dictionary of Slang

owt gens n.

[backsl.; owt n. + gen n.1 ]

two shillings.

[UK]Hotten Dict. of Modern Sl. etc.
[UK]Berks. Chron. 7 Dec. 7/1: The language of Costers. We’ve a slang, sir, and it is only know to ourselves. It puzzles the Irish and bothers the Jews [...] ‘Owt-gen’ for two shillings.
[UK]Hotten Sl. Dict.
[US]N.S. Dodge ‘Vagrants and Vagrancy’ in Appleton’s Journal (N.Y.) 6 Sept. 308: Vagrant vernacular [...] is not remarkable for originality [...] The main principle upon which this peculiarity revolves, is to spell and pronounce the substantives in any sentence backward [...] Gin becomes shilling, and owt gins two shillings. Yenork is a crown, and deenop a pound.