4520-8020 Seiko Astronomical Observatory Chronometer

Competition breeds excellence. It puts a deadline to your goals. It gives you a reference point for your abilities. It rewards effort. It punishes laziness ruthlessly. So what happens when you take famously scrupulous and detail-oriented culture, then get them to compete in horology? The competition I speak of were the Neuchâtel Observatory trials, a literal battle of chronometry in the 1960s. As you may have guessed, Seiko did alright. This watch is the apex of that effort.


Seiko improved, year-on-year, from entering in 1963 with a quartz clock (minus a misstep in 1964 finishing well outside top 10). By 1968, Seiko mechanical watches had started to outperform some Swiss peers, finishing just behind Omega overall in 1967. In the same year, Seiko won the mechanical category. The Neuchâtel Observatory competition was then curiously cancelled (this is what we call being a bad loser). However, the Observatory still continued accepting movements for testing and certification.


So Daini-Seikosha submitted 103 examples of the caliber 4520A movement, of which 73 were awarded chronometer. These were all hi-beat 36000 vph calibres, just like the prize winners. Each of these 73 movements was cased in linen-textured yellow gold with matching dial and sold with a Neuchâtel Observatory certificate. In 1969 and 1970, an additional 25 and 128 movements were certified, leading to 226 total examples produced. This is what the four lines of text on this dial represent, a sort of victory lap for doing so well that the Swiss called it off. In fact, only Girard-Perregaux and Seiko ever publicly retailed observatory certified watches until just recently with the Zenith 135 at Phillips. At the time, it cost 6x a standard 45GS. Having gone to battle on behalf of Japan, today this ref. 4520-8020 is one of the rarest and most desirable vintage Seikos ever.


This example sports a strong case with sharp bevels and a ton of that linen case texture unmarred by time. The dial is great, there’s no tritium to speak of. Its caseback shows a few light scratches but no signs of polish. If you haven’t already, it’s a worth a google to look at this movement. Sadly, not pictured. It comes from a well-regarded California retailer.

Find this 4520-8020 here from The Keystone for 45000 USD.