Fitzgerald, Augustus Frederick, 3rd Duke of Leinster (1791 -1874)
August Frederick Fitzgerald, 3rd Duke of Leinster, was the second, but eldest surviving son of William Robert, 2nd Duke of Leinster, and Emilia Olivia, only daughter and heir of St George Usher, Lord St George. He was educated at Eton and Christ Church, where he matriculated 23 October 1810 but did not take a degree. He succeeded to the title in 1804. He married, 16 June 1818, Charlotte Augusta Stanhope, third and youngest daughter of the 3rd Earl of Harrington. A Privy councillor, Lord Lieutenant and Custos Rotulorum for County Kildare, he was Grand Master of the Freemasons of Ireland. A resident landlord interested in improving his estate, he was President of The National Agricultural Society in 1841. The coronets are probably separate tools.