Definition of "eighteenpenny"

On his head he wore one of the common eighteenpenny French skull-caps, with a gawdy tassel dangling therefrom, very happily in keeping with a common fustian coat.

1836 March – 1837 October, Charles Dickens, “(please specify the chapter name)”, in The Posthumous Papers of the Pickwick Club, London: Chapman and Hall, […], published 1837