Sources differ on this date. Good 1982, p. 91 gives 1824. Wythe 1984, p. 456, who examined a great number of surviving Graf pianos, gives the following: "Most references place it around 1825 on the basis of unidentified 'contemporary sources', and Gerhard von Breuning reports seeing it in the summer of 1826. The evidence of labels and addresses ... supports a date no earlier than 31 January 1826 and possibly as late as 1827." Good, Edwin Marshall (1982). Giraffes, Black Dragons, and Other Pianos: A Technological History from Cristofori to the Modern Concert Grand. Stanford University Press. ISBN0-8047-1120-8. Wythe, Deborah (1984). "The pianos of Conrad Graf". Early Music. 12 (4): 447–460. doi:10.1093/earlyj/12.4.447.
