Square Piano by Jaeckel, J

On the makers' label beneath the soundboard, this square is called a Bandlony or "pantaleon," the name given earlier to a large hammer dulcimer popularized by the virtuoso, Pantaleon Hebenstreit. Hand stops below the 61 key (FF–f3), five octave keyboard control devices that modify the tone to imitate Hebenstreit's versatile dulcimer. The stops affect bass and treble strings separately, allowing tonal contrast between left and right hands. Credit: Met Museum