A Viking silver penny from a thousand years ago.
It says +SIHTRIC RE+ DYFLI
Sihtric, king of Dyflin (from Dubh Linn in Irish = black pool)
Sihtric (Sigtrygg Silkbeard) was king of Viking Dublin.
He was on the losing side of the Battle of Clontarf (23rd April 1014), with the Viking-Leinster alliance routed by Brian Boru's forces, but retained his kingdom.
Brian, his son and grandson all died during the battle, as did Sigurd of Orkney and Brodir of Man.
This type of penny was issued in the years immediately after the battle.