Follow-up:

I found time last night to snip out the FS-2 innards I tried to use to
replace the apparently defective original glow bulb and did the shorting
across the starter wire experiment. The lamp lit and glowed normally
(no flicker). So, the ballast is good.

That leaves me with either knowing which common starter's glow bulb to
slavage, or trying to wire in a push button SPST normally open switch
with ?? sufficient rating (to avoid rapidly ruining the contacts).

Again, to summarize, this is a 4 pin rapid start 18W G24q-2 lamp
(MaxLite model MLDE 18/41.




It's not rapid start if it has a starter, that setup is referred to as
preheat start. The lamps designed for one setup will usually work with
the other, although lifespan may be decreased.

FS-4 is the higher voltage starter intended for 30-40W T12 tubes, I
suspect it will do nicely here. That and the FS-2 are about all you can
find easily anymore anyway.

If you go with the button, something rated 250VAC at 1A ought to hold up
just fine.