Hehe - the Mellor lantern. Probably all heared it's name banded around before.
David Mellor, designer of lots of things, primarily Cutlery and Street Furnitue (quite how them two are linked, I have no idea). Ministry of Transport (MoT), now the DfT, comissioned him to design them a new type of signal to replace the Plessey Tin and SGE lanterns. In 1971-3, the Mellor lantern was eventually released en masse for all to purchase, and slowly, the decline of the tin lantern and SGE begun... Mellor lanterns were still in production by several companies in 2001, and in the early part of 2002, Siemens released thier Helios Modular signal, thus rendering Traffic Systems Co-op the only active manufacturer of Mellor lanterns, as they still are, mainly providing lanterns to Ireland and South Yorkshire, East Riding of Yorkshire, along with Norht Wales, Cheshire, and other counties.
The Mellor head is standard across the board by terms of basic design, however there are a few subtle differences between each manufacturers' concept of the Mellor design.
Anyway, theres a breif background, any questions, please fire away.