Keyboard width: FF-f3
Context: Joseph Kirkman joined the firm of his father's (Abraham Kirkman) uncle (Jacob Kirkman) in 1789. The firm began making harpsichords but by the 1760s switched over to making the new grand pianos. This firm greatly influenced English piano makers.
Literature references: Clinkscale, Martha Novak. Makers of the Piano: 1700-1820. Vol. 1, Oxford University Press, 2006.