I came upon this watch on ebay too. Caught my eye. Immediately went hunting on the forums to hear opinions.

There's no doubt it's a Kelek 1376 base with tenor-morly modification for the additional sub-seconds at 11:00. This movement was actually considered before its time in 1974 and I believe it was the smallest automatic chronograph movement.

Kelek would have supplied anybody willing to buy at the time. Their movements made it into all brands of watches. Thus, I wouldn't write this off as fake. Granted the heuer logo on the movement seems like an afterthought, the dial does appear to be authentic and the case is slightly different than the Waltham from Machismo. Notice the shape.

I wouldn't be surprised if this was a Heuer mock-up or test watch. The mid 70s are a little sketchy in terms of info from a lot of watch companies. They all started acting like pack rats. Heuer might have considered this the future look of watches. A year or two later they pursued the chronosplit with LED technology. The Kelek movement might have been usurped by digital technology.

Last, this watch is in Spain. It's not a South American seller. The guy has decent feedback. This watch might have never been released to the US and just marketed in Europe for a short time. Leonidas on the dial doesn't bother me. This might have been planned as a more mainstream product instead of giving it a race name. By this time, race names - Jarama, Monaco, Monza, Carrera - had worn thin. The future saw Pasadena, Manhattan, Kentucky and a disintegration into chaos.

It's too bad the price is cost prohibitive because I think Jeff is right - This would be an interesting piece to decipher at 500 dollars.