These are what is commonly referred to as the "hat lights".
These indicators are called "relampable" as the lens unscrews in order to replace the midget flange bulb.
They were intended for incandescent bulbs, however, modern LED bulbs are available as well.
Options for the lenses included 5 colors Blue, Amber, Green, White, and Red. Some lenses have been found with numbers stamped on the top. It seems as if there were more options in the past as to whether to have a more translucent or opaque lens. The translucent lenses pictured are no longer manufactured or available.
In GB1 the configuration is as follows Hero Gun (also referred to as the Prototype/Super Hero Gun) 1 Solid orange on gun tip 1 Solid orange by vent pushed out from the inside 1 Translucent white on gun box step
All other guns (aluminum) 1 Solid orange on gun tip 1 Translucent white by vent pushed out from the inside 1 Translucent white on gun box step
The GB2 configuration is as follows Same as above for carry over converted GB1 to GB2 packs note there is a GB1 pack that was recently sold as Harold Ramis' pack that was retrofitted for GB2 that had the translucent hat light mounted from the top by the vent although not seen in this state in GB1 movie.
GB2 Semi Hero Packs 1 Solid Orange on tip 1 Translucent white by vent mounted from the top. (this was done as the throwers were made of fiberglass) 1 Translucent white on gun box step
*note one semi hero in storage at Sony and one foam stunt pack, which was auctioned off in approximately 2008, has been seen with a translucent white cap with the number "0" imprinted on it
GBTVG gun 1 Red on tip 1 Green by vent 1 White on gun box step
The socket comes in an insulated model or a standard model but both are practically the same other than they come with extra parts for the threading section. There was also an option to have the sockets use a color code on the bottom so it would be easier to identify from the back of a panel.
This style indicator is still produced by SloanLED, known as "Model # 855-S lens type D", but it requires a special order in large quantities.Current lenses and sockets are typically available in the GBFans.com shop.
These were originally used in aircraft so they surface from time to time in surplus/salvage yards.
The correct type of bulb is a Miniature bulb midget flange base T1-3/4
