My opinion would be XF details with a couple of stray scratches on obverse which are apparent in images.

United Kingdom 
King George III (1760-1820)
Year 1799
Copper
Weight 6.3 g
Diameter 23.5 mm
Shape Round
Orientation Coin alignment ↑↓
References KM# 646, Sp# 3779
Obverse
Laureate and draped bust of King George III facing right, legend around, date below.

Lettering: 
GEORGIUS III DEI GRATIA REX
1799

Translation: George the Third by the Grace of God King

Engraver: Conrad Heinrich Küchler 

Reverse
Seated figure of Britannia facing left, trident in left hand, shield with Union flag resting on left, olive branch in raised right hand, legend above, denomination in exergue.

Lettering: 
BRITANNIA
1.FARTHING.

Engraver: Conrad Heinrich Küchler 

Edge
Plain