A rare "Digitorium" apparatus manufactured by Metzler & Co. of London, ca. 1880, as a practice device for pianists to strengthen their fingers. With five spring-loaded keys and an adjustable wrist support, the tool was patented in 1866 by Myer Marks. In fine condition with expected wear, measuring 7.5 x 6.5 x 2.25 inches (19 x 16.5 x 5.7 centimeters).

The 1900 edition of the Grove Dictionary of Music and Musicians describes the device as "An apparatus for exercising and strengthening the fingers, intended especially for the use of pianists, but claimed by its inventor, Myer Marks, to be of great service to all who require flexible and well-trained fingers. It consists of a small box about six inches square, provided with five keys, fitted with strongly resisting springs, upon which keys such exercises as the five-finger exercises to be found in every Pianoforte School are to be practised. In addition, there are attached to the sides of the box certain appliances for stretching the fingers, and a support for the wrist."