Green’s Dictionary of Slang

a wig, designed to resemble the wearer’s own hair.

1784		Morning Post (London) 21 June n.p.: Edmund, the Paymaster’s Tyburn Top Scratch is immediately to be disposed of [...] as is also Sheridan’s tragi-comic frizzled queue.
1789		J. O’Keeffe Highland Reel 18: Brush his three cock’d beaver, and powder his scratch.
1796		Sporting Mag. Jan. VII 222/2: And many a Jasey, Grizzie, Bob, and Scratch, / With this regard, pomatum turn aside, / And lose the name of powder.
c.1805		‘The Wig Gallery’ Jovial Songster 31: The henpeck’d husband wears a scratch, / His wife a monstrous Brutus.
1810		Belfast Commercial Chron. 7 Apr. 3/2: My servant, John McNamie [...] bald-headed, occasionally wears a scratch wig.
1826		W. Hone Every-Day Bk 7 Sept 631: Of all the wigs in Brighton town [...] There’s none like Johnny Townsend’s [...] (It is a scratch and not a queue).
1831		Satirist (London) 31 July 136/1: Mr. Baber [...] volunteered a song written by himself for the occasion, called ‘My own Brown Scratch’.
1838		West Kent Guardian 27 Oct. 4/4: The skull here is a capital balance to the scratch.
1840		Exeter & Plymouth Gaz. 3 Oct. 4/2: ‘You’ve taken to a wig? ’ ‘Yes [...] come to scratch at last!’.
1851		R.S. Surtees Young Tom Hall (1926) 341: Trueboy, with his scratch-wig all awry, and perturbation on his brow.
1867		Hull Advertiser 14 May 3/4: Garrick, taking off his ‘scratch’ wig, asked him [...] ‘Could you touch up this old Bob a bit now?’.
1871		Birmingham Mail 5 May 3/4: A mild and unpretending Professor, in a little brown scratch wig.
1888		Canterbury Jrnl 24 Mar. 7: We have the parson’s wig [...] the full-bottomed wig, the pigtail wig [...] the scratch wig, etc.