This stone is thought to be either a Bronze Age standing stone or an anvil stone from a later period (Roman or Medieval). It could conceivably be a standing stone that was later used as an anvil stone.
The stone stands next to the Pumpsaint Gold Mines, which were originally mined by the Romans (or so most people believe). Chris Barber alludes to the stone in his book Mysterious Wales:
Near the entrance to the area containing the Roman gold mines is a strange stone in which the five saints [Ceitho, Celynnen, Gwyn, Gwynog and Gwynaro] are alleged to have left their footprints.There are other legends relating to these five saints and their activities in the area. There are five pools in the river, which were used by these saints, and later became places of pilgrimage. I’m not sure whether the pools are in Afon Cothi or Twrch, as they both converge at Pumpsaint (another possible indication of prehistoric sanctity).
Of course the village’s name means Five Saints in Welsh.