The first shown to the public perhaps - Zenith had 1 or 2 working prototypes at that announcement. The Chronomatic group had many more prototypes at that stage but did not want to show them publicly. Having chosen the "el Primero" name, Zenith effectively forced their own hand to show it early, really before it was ready.

Jeff's article already covered this and many other details: http://www.onthedash.com/docs/Project99.html

So the real answer to who was first depends on how you phrase the question!