This cufflink contains shows both sides of a King Cnut Hammered penny. One side is on one cuff link and the other side is showing on the other. Both cuff links contain a full coin glued stongly onto the cufflink. Here's the description of the King Cnut coin that is on this cuff link ...
King Cnut reigned from 1016 - 1035 AD. He was the son of Swegn Forkbeard, King of Denmark. Cnut was acclaimed King by the Danish fleet in England in 1014 but was forced to leave. He returned in 1015 and in 1016 agreed on a division of the country with Edmund Ironsides, the son of Aethelred. No coins of Eadmund are known and on his death in November 1016, Cnut secured all England, Marrying Emma of Normandy, widow of Aethelred.
This reproduction penny is of a type known as the Quatrefoil type, struck by Grunal at Med which is short for Medhamstead (Peterborough).