It's difficult to know all of the variations a manufacturer makes on their models(I'm no a Heuer expert). One way to be reasonably certain is to open the watch's case or take it to your local watchmaker/repairer and insure that it's fitted with a Heuer or Valjoux Movm't(not exclusively) with their corresponding markings on it. Usually the watchmaker shop has cross-reference catalogs to see if a particular movement was used by Heuer.

Albert A.