4-string demonstration instrument.

Technical description: Rectangular mahogany box with short neck and wide head; two sound-holes in base of body; two legs or other supports at each side of the head, two legs or other supports at each side of the body at the 'tail end'; two pins [for two tailpieces ?]; wide bridge on belly and similar wide bridge on head; each string attached at head end to a brass right-angled lever hinged at the apex to which weights can be added so that variation in pitch with string tension can be shown.