Top posted to keep things interesting:

I bought one from Graingers last year (#6L099). They still list them in the
catalog, but they are called Ball Bearing Mandrels. I call them Bench Arbors. I
do wish the shaft was a little longer than 12", but it works just fine, driven
by a (real) 3/4 HP motor.

Joe

Lane wrote:

It's made of cast iron with holes to bolt to the bench top; its just a stand
with bronze bushings (oil caps on top) for the arbor with a pully in the
middle that you hook up to a motor behind. You can put a grinding wheel,
wire wheel or buffer on either side. There are tool rests, but no wheel
guards of any kind. I've got one and want to put it on ebay but haven't the
foggiest idea what they are called. I've Googled and searched on Ebay every
which way but can't find another one to compare it to. What are these things
called? I'm sure its an antique.

Lane