Double-action pedal harp. Inscribed 'PATENT HARP INVENTED BY J.A. Stumpff LONDON No.44 Great Portland St. Portland Place' and 'Maker/TO HIS MAJESTY THE KING OF GREAT BRITAIN'. 7 pedals, 44 strings. Back cut away to show action.
The harp has a fourchette double action: the strings pass from the peg, around an auxiliary peg functioning as a bridge, and over two discs each with two prongs (fourchettes) on either side of the string. When a corresponding pedal is depressed by one notch, the upper fourchette rotates so the prongs press against the string from opposing directions, thereby raising the pitch by a semitone. When the pedal is depressed a further notch, the lower fourchette also rotates, raising the pitch by a further semitone.