||Dating back to 1975, the first metal reflector low volt halogen lamps to be introduced by Thorn were the types M/39 and M/41, both based around a 6V 20W capsule in an open mirror stamped from steel sheet. They had diameters of 50mm and 56mm respectively, the former employing an ellipsoidal reflector profile for projection applications, the latter having a parabolic surface for display lighting tasks. Both lamps had unusual bases consisting of a pair of metal tabs to which flexible electrical cables could be connected.
In order to realise a more user-friendly format for general display lighting applications, the M/53 version shown on this page was introduced by Thorn in 1982. It represented a number of key development steps which many later lamps came to rely upon. Perhaps most importantly, it was the first long-life 20W halogen source designed for operation on a 12-volt supply. The 12V 20W filament is made from wire of very fine diameter, and the rate of attack of the cold ends by the halogen cycle previously meant that a long life could only be achieved with 6V lamps which employ a thicker wire.
Secondly, this lamp was the first product to feature a sealed design with a glass lens closing the face of the reflector. Low voltage halogen capsules are typically cold-filled to pressures in excess of 4 bar and there exists a risk of explosion during operation. Finally, it marked the first introduction of the SBC cap for halogen reflector lamps. This presented a much more user-friendly option than Thorn's previous products with metal tabs, and is considerably easier to install than types using the two pins of the halogen capsule as the base. M/53 enjoyed only a brief period in production, being superseded in the mid 1980s by the Lightstream MR16 range with dichroic reflectors.