MRA stands for Maria Regina Angelorum (Mary Queen of the Angels). The stone beneath the IHS MRA monograms is indeed inscribed with the date 1691. It also has the monograms of Patrick Leslie and Mary Irvine of Drum, his second wife. There is a buckle between the P and L from the coat of arms of the Leslies of Balquhain and a holly leaf between the M and I from the coat of arms of the Irvines of Drum. The ancestral home of the Leslies was Balquhain, and one of the houses there also has a stone inscribed with the IHS MRA monograms, but it is dated 1677. For more more information, see an article by P. Dransart and N.Q. Bogdan called 'The material culture of recusancy at Fetternear: kin and religion in post-Reformation Scotland', Proceedings of the Society of Antiquaries of Scotland 134 (2004), pp 457-470.
