Green’s Dictionary of Slang

of people, objects, experiences: the best of a type or style, the superlative.

1847		A. Smith Natural History of the Gent 6: He evidently imagined that he was ‘rather the Stilton than otherwise’ —‘Stilton’ or ‘cheese’ being terms by which Gents imply style or fashion.
1851		Bell’s Life in Sydney 12 July 3/1: He is not, to say, a gentleman [...] He is not, to say, the Stilton, because he is a very indifferent representation of thal highly pleating masticatory preparation of the whey.
1856		H. Mayhew Great World of London 5: Besides he wants a more nobby crib, as the one he hangs out in now is only fit for some pleb or cad. It really isn’t the stilton.
1859		Hotten Dict. of Modern Sl. etc. 102: ‘That’s the stilton’, or ‘it is not the stilton’, i.e. that is quite the thing, or that is not quite the thing;—polite rendering of ‘that is not the cheese’.
1862		Mayhew & Binny Criminal Prisons of London 5: He wants a more nobby crib, as the one he hangs out in now is only fit for some pleb or cad. It really isn’t the Stilton.
1869		‘Walking in the Zoo’ in De Marson New Singer’s Journal xxxv. 246: The Stilton, sir, the cheese, the O.K. thing to do, / On Sunday afternoons, is to toddle to the Zoo.
1877		J. Diprose London Life 39: It really isn’t the Stilton.
1903		Truth (London) 18 June 1678/3: Slang terms: [...] slap-up, slick. splendiferous, stayer, stilton, stunning, swell [etc] .
1909		J. Ware Passing Eng. of the Victorian Era 234/1: Stilton (Peoples’, 1850 on). Distinction. Synonym for cheese (see). She was the real Stilton, I can tell yer.