1851 Great Exhibition: Official Catalogue: Class X.: Joseph Harwar
493A. HARWAR, JOSEPH, 28 Bloomsbury Street — Manufacturer.
Pianoforte with transposing mechanism, metallic equilibrium string frame, adjusting tension rods, and improved sound-board, fitted up in newly designed case with sliding front.
[The first transposing pianoforte was invented by a German named Rolla. The keys in this instrument were shifted; the modern system is incomparably superior.— H. E. D.]