After a quick look at the parts diagrams at Sears Parts Direct, it looks like the 18024 comes with a separate foot controller, which the 18023 doesn't.
Maybe the 18023 only came in a cabinet, which has the knee control attached to it. That's how mine is.
Actually, the 18024 is the only model out the five versions of the 1802x that has a separate foot controller, so it's hard to say.
Last edited by mlmack; 02-01-2015 at 01:54 PM.