Green’s Dictionary of Slang

1. (also susheroon) a crown piece, five shillings [OED suggests that this is ‘erroneous’].

1859, 1860		Hotten Dict. of Modern Sl. etc.
1863		Story of a Lancashire Thief 9: There was Downy, a Turkey merchant in a small way, who had such a feeling for tusheroons that he was always changing his tanners and stags, and aldermen, into them.
1873		Sl. Dict.
1884		Henley & Stevenson Admiral Guinea II i: Old Pew’s too smart to be bammed with a soft half-tusheroon.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1929		Advertiser (Adelaide) 25 Oct. 32/8: The ‘screever’ (pavement artist) is informed where he can loan chalked pictures for a ‘susheroon’ (five shillings) a day.

2. see tosheroon n.