E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Half-faced Groat (You).
You worthless fellow. The debased groats issued in the reign of Henry VIII. had the kings head in profile, but those in the reign of Henry VII. had the kings head with the full face. (See King John, i. 1; and 2 Henry IV., iii. 1.)
Thou half-faced groat! You thick-cheeked chitty-face!
Munday: The Downful of Robert, Earle of Huntingdon (1601).