4102D valve in original box. Bakelite mount. Written on box " Det. Amp. valve for Pos V3 4102D". 4102D valve in original box. Bakelite mount. Written on box " Det. Amp. valve for Pos V3 4102D".
The bulb is round with a green tinted tip. The filament inside of the fulf contains two grids sandwiched between two metal plates. There are markings on the Bakelite mount that say 'Standard Telephones and Cables Ltd, Patented in Great Britain, 17580/15, 161619, 180090, 4102D. The bakelite mount has a 4 pin base.
The technology was patented and first developed by Western Electric. They were manufactured after 1925 as Standard Telephone and Cables Ltd.
Asbestos Inspection - Non-Asbestos.
