Watch List notes:

THE COLLECTION OF A CLASSICIST, BRITISH COINS, George III, Copper Halfpenny, 1770, struck on a thick flan, laureate and cuirassed bust right, rev Britannia seated left with spear and shield, date in exergue, 13.54g (cf Peck 893; S 3774). Obverse rim nick, otherwise well struck, extremely fine, toned with a little lustre.
This coin is about 4g over the usual weight and much thicker than usual.

Estimate: £300-400