Interesting indeed!
Besides this forum, I also hang out at the vintage Seiko and Zenith forums - it's interesting that each forum have their own point of view about this, and perhaps unsurprisingly, each think their's is the first.
The Zenith folk say Zenith was the first to announce, and showcase, a working c.3019, so they'll forever be the first.
The Seiko folk say you could walk into a store in Ginza in the spring of 1969 and purchase an automatic chronograph, the Seiko 6139, and that's earlier than anywhere else in the world.
Doesn't matter to me, cos I collect all three!
But in addition to the Zenith advert and Jeff's excellent article, this should be required reading:
http://www.watchtime.at/archive/wt_2009_06/WT_2009_06_102.pdf
Another interesting angle to all this is that, unlike Zenith and Heuer, serial numbers of 60s Seikos document not only the year, but also the month of production!
It's relatively easy to find a Seiko 6139 automatic chronograph with serial number dating to March 1969!
Here's mine (serial number 93xxxx, indicating March 1969), together with it's other Seiko, Zenith and Heuer brothers!

ben
Singapore