My first reaction was "how could they have reached 1704 by 1989".

I have Whiteside Express which I believe was built in 1987, but it's sail number is 1659. That made me doubt that you have the same Zeus.

But I've looked into it a bit more and I see that Bob Wilson won the Nationals on Shannon (now Itchy) in the 1989/90 season, and that boat's number is 1736.

That means around 80 boats were launched in 3 years. Wow! Any class that could do that these days would certainly get noticed.

It looks like Zeus also took the National Title in 1991. Not a bad run.