Another thread on here mentions the NE-2 neon bulbs. I remember those
going back to the 60s. They have never changed, but worked well for
testers or indicators if you did not want brightness.

But I always wondered, was there a NE-1, or a NE-3? I always wondered
why they are called NE-2? I have never seen any other number after the
NE-.

One thing about them, if they were used for continuous use, such as a
nightlight. Eventually they get weak and die. They usually flicker
first. I had a nightlight with one of them that eventually did no longer
light, but if the room's lights were turned on, then it would light. I
recall showing that goofy thing to a friend and telling him it was
retarded. We got some good laughs out of that thing...