The Ancient British stater featured here was unearthed by Brian Mansfield and it has been recorded on the Celtic Coin Index. As can be seen from the illustrations, rather than being made of solid gold it has a base metal core, which would originally have been completely covered by a layer of gold.
This stater is a plated example of the AVNT COST left type of the Corieltauvi. On the obverse only vestiges of the design can be seen and only about 20% of the gold plating has survived. The reverse is much better: the left facing horse is nearly complete, AVN can be seen above it and about 75% of the gold plating is still intact.
In Ancient British Coins it is listed as number 1929 as the Aunt Cost Left type. In the Standard Catalogue it is number 402.
The type is very rare but the state of preservation of this plated copy leaves much to be desired. However, I’ve occasionally seen base metal cores of Ancient British gold staters on offer at around £100. This example still has a good proportion of gold on the best side, so to a keen collector it shouldn’t be worth any less than £150.