1982 Osram GEC MB/U 400W

Medium pressure mercury vapour lamps traditionally came in tubular envelope. However High pressure lamps traditionally cane in bulbus to eleptical bulbs. The bulbus bulbs were used as first of all standard high wattage GLS envelopes could be used and as well as frosting or early phosphor coating could be applied to prevent glare in the first and ad red light emissions in the latter case. However eventually with advancements in technology it become possible to to build higher wattage high pressure lamps. These lamps quickly replaced the older medium pressure lamps because of their higher efficiency, especially when pared with modern phosphors. However these lamps generally employed Elliptic outer bulb as the phosphor would overheat in a tubular envelope.

While in countries like germany that lead to the replacement of the older medium pressure fittings because the new lamps could physically not fit in some fittings, the UK chose a different approach. In the UK an MB/U lamp in clear tubular shape was offered by all major manufacturers. These lamps allow a drop in replacement of the older lamps. These lamps were offered for a very long time after the discontinuation of the classic medium pressure lamps, with these lamps still beeing available into the 1980’s.

This particular lamps is a 400W lamp made by the General Electric Company of England in Shaw, Oldham in april 1982