lop, n.² — Green’s Dictionary of Slang

lop n.²

[ety. unknown, ? link to dial. lop, a flea, i.e. the coin’s innate worthlessness]

(Anglo-Irish) a penny.

1953		F. O’Connor Coll. Stories (1981) 429: ‘Well, give me a lop anyway,’ he begged, and she did give him a penny .
1993		M. Verdon Shawlies, Echo Boys, the Marsh and the Lanes 35: Not being a sawney, he spotted a way for doing foxers and soon he had loads of lops.
1996		(con. 1950s) C. Kenneally Maura’s Boy 9: Here’s a lop for a candy apple.