There are a couple of occasions where starting numbers are reserved, like the aforementioned Chronomatics. And we do find models are blocked together, but that doesn't necessarily mean that the bloack started at xxx000. But we simply don't know enough to definitively say "This block starts here" except in a very few cases and even then, we would be extrapolating somewhat. They don't always "reset" the numbering for a new batch of a different model - there are some instances where a block of 1000 will cover more than one model - 393xxx covers quartz Carreras, the Monza and the Modena for example.

The serial number quoted (assuming it does indeed have an end digit!) comes after a group of rebranded manual Autavias (Primato, Zodiac) and before some Heuer automatic Autavias so seems a good enough fit to me.