Ok, this is embarrassing but I've got to admit the truth when I made a mistake.
I have the 1/2 hp Vertex spinner, not the 1/3 hp model. The motor's label is on the side where I can't see it without removing the whole machine out of its cabinet. I found my original receipt from November 2001. I paid $189.95 + $10 shipping.
For some unknown reason I always assumed I had the 1/3 hp motor. Oh, well, confession is good for the soil.
FYI it's still going strong.