Information about effigy: King George III - Laureate Head by W. Wyon

Laureate head of King George III facing right, by William Wyon.

This looks very much like the small laureate head by Benedetto Pistrucci, by its slightly different - most noticeably in the tails of the ribbon tying the Kings hair.

On circulating coinage, a similar (yet different...) portrait seems to have been used only on the 1817 half crown.

On the 1817 "Three Graces" pattern crown, this one is signed by William Wyon.

God version of The Three Graces pattern crown

United Kingdom / Crown Pattern 1817 The Three Graces

Apart from the silver prototypes, a gold version was made - probably intended as a curio, as the crown was never supposed to be a gold piece.