Green’s Dictionary of Slang

netenin gens n.

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

19 shillings (95p).

[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[UK]Sl. Dict.
[Aus]Sydney Sl. Dict. (2 edn) 11: Net Egin Gen - Nineteen shillings.