Illustration of the devolving bust of Apollo and the reverse Charioteer from the gold Philipp II Stater to the Durotriges Stater:

Thank you CGB Monnaies XV for this illustration

Apollo to a fixed Durotriges abstraction, hallowed by tradition

Philip II of Macedon issued this gold stater which, paid to Celtic mercenaries, was imitated and did evolve for 300 years. In Pre-Claudian South West Britain the Durotriges iron age tribe adopted and adapted the continental staters (like the Ambiani) in a gold stater design which stayed fixed for a hundred or so more years as the stater debased to pale gold, silver, debased silver then billon.

Philip II gold stater
“This piece, an excellent example of an early Philip II stater, depicts the god Apollo on the obverse, and on the reverse features a charioteer, with Philip’s name appearing in the exergue. This design is considered the standard Philip II gold “type,” as the design combination remained essentially unchanged for as long as these coins were struck.”
Thank you NGC Ancients article for image and text

CELTIC, Britain. Durotriges. Uninscribed.

CELTIC, Britain. Durotriges. Uninscribed. Circa 65 BC-AD 45. Pale AV Stater (6.01 g, 6h). Durotrigan E, Abstract (Cranborne Chase) type. Devolved head of Apollo right / Disjointed horse left; pellets above, pellet below, pellet in lozenge above tail, [zigzag and pellet pattern between two parallel exergue lines]. Van Arsdell 1235-1; cf. SCBC 365 (’Silver Stater’). Choice EF, toned. Exceptional early issue with higher gold content.

“Like many Celtic gold staters throughout Europe and Britain, the designs of this series are based on the prototype of the gold staters of Philip II of Macedon. Although very early issues attempted to copy the types exactly, most of these Celtic imitations quickly added elements of local style. The original types, head of Apollo / Nike in quadriga, soon devolved into schematic forms that were quite indistinguishable. Many later series, such as this one, began from a series that already had devolved these types, and even though they continued for many decades, the types saw little, if any, further development. Though the types remained fairly constant, the metal quality continually degraded over time, and it went from a gold to billon coinage by the time it ended in the mid-1st century AD. The higher weight and gold content of this piece clearly place this coin at the earliest stage of this large issue. While Van Arsdell’s general listing for his 1235-1 type encompasses all metal types, SCBC only lists the silver and billon.

Thank you CNG for image and Text