Key & Plug Assembly No. 9, CDN, made by WESTCLOX. This key is found in the "case spare parts no. 5 C" as supplied with the WS 19. It was also supplied with WS 52.
This example is in good physical working condition, however, someone has decided to repaint the cover with Hammerite. Mounted on a mahogany plinth and cabling terminated with standard 1/4ins Jack plug.