Green’s Dictionary of Slang

a sovereign.

1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1890–1904		Farmer & Henley Sl. and Its Analogues VI 13/1: Remedy [...] (Old Cant). – A sovereign.
1905		Exeter & Plymouth Gaz. 4 Feb. 5/6: A sovereign has been rechristened a ‘glistener,’ a ‘goldfinch,’ a ‘mousetrap,’ a ‘new hat’ [...] a ‘remedy,’ a ‘stranger’’.
1919		Smith’s Wkly (Sydney) 7 June 9/6: Slang of Money [...] A sovereign is a ‘glistener,’ ‘mousetrap,’ ‘new hat,’ ‘quid,’ ‘remedy,’ ‘stranger,’ ‘thick ’un’.
1925		Mail (Adelaide) 23 May 23/4: The sovereign has been variously called a ‘glistener,’ a ‘mouse trap,’ [...] a ‘remedy,‘ a ‘stranger,’ a ‘bean’.