CARRERA GRAND PRIX => Heuer Ref. 13-1 ?!

Hi, I am interested in this watch, according to the seller it is a "Carrera Gand Prix". I assume it's a Heuer Ref. 13-1 with a special dial? Or how did the Carrera Grand Prix and Heuer relate to each other? Maybe someone has some information about the watch or if it could be a Heuer, Lanco or Primato. Thanks.