Claim: Lord Duffus is an extinct title made by Charles II for Alexander Sutherland wherein the last two Lords Duffus were also baronets and the lordship became extinct when the sixth Lord Duffus died.
Evidence: The title Lord Duffus was created by Charles II in the Peerage of Scotland on 8 December 1650 for Alexander Sutherland. The title is now extinct, although there may be male-line Sutherlands descended from earlier lairds of Duffus. The last two Lords Duffus were also baronets, of Hempriggs in the County of Caithness (3rd and 4th). The lordship became extinct on the death of the 6th (titular 7th) Lord Duffus on 28 August 1875. 
Alexander Sutherland, 1st Lord Duffus (d. 1674) (son of William Sutherland, 10th of Duffus) James Sutherland, 5th Lord Duffus (1747-1827) (restored 1826), who died unmarried. He eloped in December 1771 with the seventeen-year-old Lady Mary Hay, the daughter of the Earl of Erroll, Hereditary Lord High Constable of Scotland, and the wife of Major-General John Scott; she was divorced by her husband, Sutherland's colonel at the time. He abandoned her, never married, and recognized 10 illegitimate children in his will. However, he is said to have at least 60 illegitimate children. The barony was claimed by the nearest heir male (and also by the 5th Lord's nephew): Benjamin Dunbar, 6th Lord Duffus, 3rd Baronet of Hempriggs (1761-1843), grandson of Sir James Sutherland-Dunbar of the 5th Lord Duffus This man, together with his son, unsuccessfully petitioned the House of Lords in 1838 to be granted the title and the seat in the House of Lords, but the petition was not acted upon. (A challenge was mounted by the Rev. Eric Rudd, apparently the sole surviving nephew of the late 5th Lord. He was the son of Elizabeth Sutherland by her third husband Rev. James Rudd (d. 23 February 1827, aged 83) He was succeeded de facto by his son: George Sutherland Dunbar, 7th Lord Duffus (1799-1875) (extinct 1875) used the title of 7th Lord Duffus, but was also known as Sir George Dunbar of Hempriggs, 4th Baronet.