Green’s Dictionary of Slang

neetexis gens n.

also netexis gens
[backsl.; neetexis n. + gen n.1 ]

16 shillings (80p).

[UK]Hotten Dict. of Modern Sl. etc. 128: NEETEXIS, or netexis gens, sixteen shillings.
[UK]Hotten Sl. Dict. [as cit. 1859].
[UK]Sl. Dict.