Estimated Date: 1875
Name: Sphygmograph, Richardsons
Manufacturer: Allan and Hanbury
Description: 5” x 3“x 2” leatherette case contains device similar to Dudgeons but with 2” rod which extends and has an adjustable weight to adjust pressure rather than screw spring. The body of the instrument is 2” long, there is a 2’ sq. clockwork mechanism to turn the smoked paper on a rod drive. Marked #294 in base. Virtually the same instrument can be viewed on this site another model. out of the box.
Reference 1: 122