Watch List notes:

BRITISH COINS. Other Properties. George III, Halfpenny, 1775, contemporary forgery with medal alignment, laureate and cuirassed bust right, rev Britannia seated left on globe with shield, spear and spray of leaves, date in exergue (cf Peck 908; cf S 3774). A few light surface marks and struck slightly off-centre on the reverse, toned with a hint of lustre, practically as struck.
this would appear to to be an expert forgery from a Birmingham workshop

Estimate: £100-150