The Walters Model 18-K. Walters Variable Fulcrum single current landline key. Walters Electrical Co. London. 19th century.

Little known about this interesting key. Believed to be a WALTERS 18-K. The style is unique as you can see from the photos. The wooden base measures 6 & 3/4" by 3" ( 172mm x 76mm), the knob is - I think - ebony, and parts lacquered brass, c 19th century.

The photo below shows the Gap adjustment (G) and the clever Tension adjuster (T) that is spring loaded and when slid towards the operator, increases the tension.

Featured on the front cover of Morsum Magnificat magazine number 71.