Circular ivory musical volvelle stamped EARNSHAW’S PATENT. It was
used to transpose and compare musical keys, and works in a similar manner
to a circular slide rule, in that a chamfered ivory disc moves over another
ivory disc. The stamped and engraved markings are heightened in black, red
and ochre.
It was patented in 1869 by Alfred, George, Edward and Frederic Earnshaw,
all of whom were clerks.
Diameter of disc 1.9 inches (4.9cms). Very good condition. English c.1870.
Ticket price £390. Email me here
See:British Patent Specification No. 2647 of 1869.
S. Earnshaw, Description and Use of the Key of Musical Keys,
N.D. (1869?)
