Probably Viking, as the drum lock was used in the slave trade and is different from a rigid bolt lock as used on doors and chests. The lock contains an internal V spring which requires compression by the rectangular opening in the key bit, to free the shackle. Forged iron, 4 5/8” length with circular eye attaching a ring. The ring suggests it was used with other keys, consistent with slaving. During the period, Vikings were by far the most active slavers on the European continent.