The Resolution:

I emailed Leviton and a local electronics parts store about identifying
the mystery switch. Leviton responded to say that they stopped making
industrial switches of that kind many years ago. I suspected that might
be true, as they seem to mainly be into residential light switches
these days. The local store never responded. I decided to take a chance
and I bought a switch from Amazon that seemed to be similar to some
suggested in this thread. It wasn't expensive.

I installed it today. It did sorta work, but the light was only off or
on, no dim setting, and you had to push the button 4 times to cycle
back to Off. It was adequate, but I didn't like the way it worked or
felt.

Then I opened up the old switch - not hard to do, just pry open three
metal tabs on the back. The mechanism inside is pretty clever - pushing
the button pushes a spring-loaded corkscrew-shaped tab that rotates a
little ratcheted wheel against the three wire's contacts. Each push of
the button advances the wheel one notch. It was obvious what the
failure was: the little spring had finally, after 40 years of use,
broken. I ended up cannibalizing a ballpoint pen for its spring, which
I cut to length. I thoroughly cleaned all the little parts, lubricated
it with a tiny dab of Vaseline, and reassembled it. Its click felt
right, so I re-installed it in the range hood, and it works fine! With
some luck it will last for another 40 years, and now I know it can be
fixed with a ball point pen.

So, all's well. Thanks to everybody for your thoughts and suggestions.


On 15 Jul 2018, Nil wrote in
alt.home.repair:

I hope someone here can help me identify this switch or an
equivalent one. It's from an old (late '70s) GE range hood. There
are a pair of pushbutton switches - one controls the fan - push
once for high speed, push again for low, push again for off. The
light switch is similar - push once for bright, again for dim,
again for off. The light switch has failed. It's a mechanical
failure, it won't pop out any more. I will replace it when I can
find another of its kind.

This one is a Leviton brand. It looks like the push or rotary
switches I've seen on many light fixtures. I see some such
switches referred to as "canopy" switches. Engraved on the front
copper face is:

UND.LAB.INC.LIST.
1A-250V
3A-125V
3A-125 V.A.C.-L
SA (in a circle)

Can anyone help steer me in the right direction? Pictures at:

http://rednoise.vacau.com/temp/switch/