Pennies from Heaven

Our property boundry on the East side is marked by an old Purbeck stone wall. Mounted on top in the style of a dragon's back are more stones, some covered in moss.

I noticed that someone had dumped a small pile of coins between the upright stones.

Why would someone find the burden of 18 coins too much for their pocket and leave them on a wall?

Note too, the front face of the middle stone has the remains of a fossil (the grey bit) embedded in the stone.