[broadgage]

IME the flat shaped torch bulbs often had the rear part of white opal glass so as to function as a basic reflector.
Primarily to direct the light forwards in an appliance without a reflector.

There used to be a popular type of wall mounted light that used a 3 volt cycle lamp battery and an opal backed, flat shaped bulb.

In homes without electric lights, one of these battery lights mounted just inside the front door was easily located and turned on by touch.
In houses with electric lights, one of these battery lights could usefully be mounted next to the fusebox.

Also popular for lighting sheds, garages, outside toilets, and in the last war for domestic air raid shelters.

AFAIK these opal backed flat shaped bulbs are no longer made, they command a high price as some vintage model cars used them as headlights.

I have seen these bulbs in red, possibly to preserve night vision, but never in blue.