A keyboard that bows strings instead of hammering them.
[edited to add] The accompanying description plate can be found here. (below is quotation)

Inv.-Nr. 73492
"Phonoliszt-Violina" Reproducing Piano with 3 Violins
Ludwig Hupfeld AG Leipzig, around 1912

Numerous attempts since 1850 to reproduce the playing of a violin
mechanically were thwartet by bow that requires guiding or
the inability to replace it. This instrument reproduced the playing
of famous virtuoso of the piano and violin almost perfectly.

The difficulty in producing the sound of a violin mechanically was solved
by the company Hupfeld AG Leipzig with the desing of a circular box
that rotates around the violin. Hupfeld used three real violins, with strings
drawn to the bow with suction.

With increased pressure, violins sound louder, making crescendo and
decrescendo possible. Levers activated by bellows replace the fingers of
the player. Three special bellows produce the vibrato. The violins are
linked to a Phonoliszt piano that is operated by a suction-system.

Interchangeable perforated paper-roll,

3 violins with one sounding strang each in d1, a1 and e2,

rotating circular bow with approx. 1,300 tangentially strung horse hairs,

pianino with keyboard range A2-c5, one to three strings,

2 pedals for shortening the hammer blow distance and damping.