Just a question my boss asked me.
IIRC, only one of the filaments will light, instead of both.
I believe it’s the brighter one, based on what happens when you plug a normal bulb into a 3-way socket.
Shouldn’t break anything
No. The contacts that shunt electricity to the second filament are not present, so only one filament lights, as opposed to either 1, the other, or both in a 3-way bulb.