"it's a George III copper halfpenny (which were minted 1769-75)"

Nigel, DO YOU REALISE WHAT YOU HAVE FOUND !!!

If you aren't joking that coin could have been dropped when the spoil from the Northumberland/Drax shaft was dug in 1776-7 and the spoil was being slung down the sides by the miners !!!!

That could be a part wage payment for digging the dreaded shaft, that caused the collapse, that NT found, that EH put polystyrene in, that called the meeting etc...that Jack built...

I can see the Headlines:

HA FINDS UNIQUE ARTEFACT (Times)

CERNE GIANT LOOKALIKE SPENDS A PENNY (Sunday Sport)

The museum caption will read like a medal : found by Heritage Action in the cause of duty, Silbury Hill 2004

It will be in the campaign collection Silbury 2000-2020 !

VBB