Robert III, born John Stewart, was King of Scotland from 1390 to his death. He was known primarily as the Earl of Carrick before ascending the throne aged around 53 years. He was the eldest son of Robert II and Elizabeth Mure and was legitimised with the marriage of his parents in 1347 (Wikipedia).

BNJ References:

P. Higginson,    ‘An unrecorded halfgroat type of Robert III of Scotland, 82 (2012), 226-7.