I'm organizing a lot of components and don't know what this is. Hooked up to PS at low voltage and nothing happened. I can't tell the anode from the cathode. What is it?
Looks like a neon light. They need a fairly high voltage to light up.
Like, 90Volts or more. You can use them on 110VAC with just a small series resistor.
This is an example:
A quick look at a datasheet for the NE2 says it needs 95VAC or 135 VDC to light up.
So, you can run it on DC, but you'd need an unusual power supply to do it.
Looks like a neon lamp to me. You need higher voltages to light it up.