Green’s Dictionary of Slang

£1 sterling, thus half quidlet, 10/- (50p).

1890		Music Hall & Theatre Rev. 15 Feb. 7/1: The occasion was a great success, and the golden quidlets plentiful.
1901		Marvel XV:386 Mar. 1: ’E give us the quidlets ter do a bit o’ fightin’, if need up.
1905		Sporting Times 25 Feb. 5/2: Three quidlets apiece, or p’r’aps five—p’r’aps ten— / And so the smacks went rolling.
1907		Sun. Times (Perth) 10 Feb. 4/7: he had spent his quidlets shining / With the maidens he’d been wining.
1911		J.W. Horsley Memoirs of a ‘Sky Pilot’ 253: ‘Quidlet,’ for half a sovereign.
1914		Dubbo Liberal (NSW) 4 Dec. 6/3: The trio toed the mark in the hall of justice, the former finding it necessary to plank up five quidlets.
1912		Sport (Adelaide) 22 June 10/2: They Say [...] That That the mob are warned against lending half-quidlets to G.F .
1926		Derby Dly Teleg. 7 Apr. 3/3: Every coin has some slang name [...] tush [...] quidlet [...] fadger.