Signalling Equipment Limited or SEL of Merit House, Potters Bar, Middx. Telephone: Potters Bar 2262-3. Cables: "Sel. Potters Bar"
1943 June. Advert in Flight magazine for Morse Complete Practice Unit. 
1947 Listed Exhibitor - British Industries Fair. Manufacturers of 4/6 V Motors, Transformers, Electrical Outfits, Model Dynamos, Induction Coils, Miniature Electrical Equipment, Microscopes, Magnetic Compasses, Telescopes, Theatre Glasses, Model Stationary Steam Engines, Morse Practice Keys and Buzzers. (Olympia, 3rd Floor, Stand No. K.2420)