Columbus FMX tubing?
 

I've never heard of Columbus FMX but I am assuming that it was/is a private label tubing made used exclusively on Fondriest bicycles. (and I am also assuming that if it is private label it is probably not top of the line Columbus, or Fondriest would have slapped SL or SLX stickers on their frames instead.)

But has anyone ever heard of FMX or know what standard model this would correspond to?

It is Columbus SLX - the writing on the sticker is a clue, as are the spirals inside the tubes.