Green’s Dictionary of Slang

a red-skinned apple, considered inferior produce but capable, with judicious polishing, to be sold as something better.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 61/1: A cheap red-skinned fruit, known to costers as ‘gawfs,’ is rubbed hard, to look bright and feel soft, and is mixed with apples of superior description.
1870		Hotten Sl. Dict.
1873		Sl. Dict.