Two lamp mounting variants seem to be have been employed on the mushies. This I presume was for the two different variants of the small helmet mounted Premier carbide lamp. Some Premiers have the "blade" fitted to engage the helmet bracket, some, like mine, have a sturdy wire "hook" and two springs grips at the side.
The hook fits into a hole that exists in the fibre above the bracket. The two springy clips grip the side of the bracket support. With the proper variant, the rubber bumper dooferiser on the lamp base just sits snugly on the peak. No butchery required!
Were there not 2 manufacturers of the mushy ? Huw Wood (as prev. mentioned ) and Cromwell (??).
Who threw the overalls in Mrs Murphy''s Chowder ??