3rd can run at 100 rpm (100 rpm is really slow for a lathe). There are

For a lathe spinning small spindles, perhaps. Or if you've been
brainwashed into thinking that the reason cheap lathes never have a low
end below 500 RPM is a design decision based on something other than
$cheap. I go below 100 rpm just about every time I use a lathe that is
capable of doing that, and I've gotten sick and tired of lathes that are
not.

YMMV, DWYL, etc...

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