^John Ainsworth (b. 1777) says in his book Walks around Bury (1842) that he saw this picture in 1842, and that it appeared to show the inventor's son who he knew "very well". Although Ainsworth knew the son as an old man, and could not have met the inventor himself, Lord (1903) wrote that this "settles the question of doubt as regards the portraits which Lieut.-Col. Sutcliffe put into circulation as a portrait of his great-grandfather" (the fly-shuttle inventor) because Ainsworth is a more reliable source than Sutcliffe, who originated the claim that the elder John Kay is pictured.
^Mann, J. de L. XXII: The introduction of the fly shuttle. The cotton trade and industrial Lancashire, 1600–1780 Book V. Manchester University Press. January 1931: 449. ASIN B0006ALG3Y. This son was known in later life in Bury as "Frenchman Kay," and the portrait supposed to be that of the inventor is really his. As well as the identification of the sitter given by John Ainsworth, the "French" clothing and tricorne were characteristic of "Frenchman" John Kay in 1790s Bury (where he was considered a "fop" -see Lord (1903) pages 91–92).
^J. B. Thompson's 1964 summary in The achievements of Western civilisation says "date of death unknown". Nobody has yet found exact records or year of his death, though all sources agree it occurred in France between 1764 and 1780. His final year is often given as 1764 (for instance, by the London Science Museum) and often as 1780 (e.g. the BBC's History of the worldgives a 1780 death date in the South of France at age 76). Lord (1903) was skeptical that Kay reached 70. And, in the Bury Times (27 December 1902) Lord wrote "The death of John Kay, in Paris, occurred in 1767 or 1768" (see: Bygone Bury p. 108). Lord acknowledges that no Paris death registration exists for John Kay between 1750 and 1770, but says that this is because "documents of all kinds were destroyed during the Commune revolutionary days" —see Lord (1903) p. 169. Mann (1931) reports a July 1779 letter from Kay (largely ruling out earlier dates) but says that he very probably died shortly after the letter was written and that the author of Thoughts on the Use of Machines (1780, probably Dorning Rasbotham) makes a "natural error" in writing that Kay was still alive in 1780.
^Lord (1903) p.91, reports the 1850 recollections of John Kay's great-granddaughter, who called the Kays of Park "Jacobites... High Churchmen in Religion and Radical Reformers in Politics."
^Lord, J. VI: John Kay, Inventor of the Fly-Shuttle. Memoir of John Kay. 1903: 96. OCLC 12536656. He married in 1725, Anne, the daughter of John Holte, probably a near neighbour, and set up housekeeping at Park.