Featuring in this week’s “Full Frame” is the movement of the Grand Seiko 4580-7010. A slightly smaller – yet no less impressive – image than usual, since when tilting and swinging the focal plane to the extent that it is in this shot, I can’t get as much magnification.
Before getting onto the photograph itself, this is probably a good opportunity to clear up some confusion that is out there as to the number of 4580 movements that were created, and where they ended up.
Following the end of the Neuchatel Observatory Chronometer trials, Seiko submitted for certification a number of 4520 and 4580 movements in the years 1968 through to 1970.
In 1968, 103 examples of the 4520 caliber were submitted, of which 73 passed certification.
In 1969, 30 examples of the 4580 caliber were submitted, of which 25 passed certification.
In 1970, a further 150 examples of the 4580 caliber were submitted, of which 128 passed certification.
That much is widely written up and accepted. Where the confusion lies is how these movements were cased up and sold.
All 73 of the certified 4520 movements were cased up and sold as “Seiko Astronomical Observatory Chronometers”.
Pictured above is an example of the Astronomical Observatory Chronometer once owned by the author. It is important to note that this watch is not a Grand Seiko. Whilst sharing a case from the Grand Seiko 4520-8010, it was made, branded, and marketed as the Seiko Astronomical Observatory Chronometer.
Whilst it is true that all there are a number of different watch models containing the astronomical observatory certified chronometer movements (note – no capitalisation), it is the author’s strong opinion that only this watch pictured above – the 4520-8020 – should be referred to as “the” Astronomical Observatory Chronometer. And it most definitely should not be referred to as a “Grand Seiko”!
So. That accounts for the 73 examples of the certified 4520 movements. But what of the 153 certified 4580 movements?
In my write-up of the 45GS series vintage Grand Seiko watches in my collection which can be found here, I close off the article with a plea for clarifying what the situation was with the 4580 movements –
“There are many conflicting write-ups on the internet regarding the 4520 Astronomical Observatory Chronometer and the 4580 Very Fine Adjustment movements.
Depending on what you read and where, the story is either –
ALL Neuchatel certified 4520 movements (73 pieces) and 4580 movements (153 pieces) were used in the Seiko (not Grand Seiko!) Astronomical Observatory Chronometer that has the model number 4520-8020. Thus, there are supposedly 73 AOC’s out there with 4520 movements, and 153 with 4580 movements – making for a total of 226 Astronomical Observatory Chronometers. Then, additional 4580 movements were created (how many is not stated) which were used in the 45GS VFA’s.
The alternative interpretation is that only the 4520 movements were used in the AOC, and the 4580 movements are those that you find in the 4580 VFA’s. In other words, there are just 73 AOC’s, and 153 VFA’s.
If anyone reading this can clarify what the true situation is (with proof!), I’d be very appreciative – please don’t hesitate to leave a comment below.”
Well, as it turns out, neither of the above interpretations are correct. Following a long conversation with one of the most respected Japanese dealers in vintage Grand Seikos, it can be confirmed that indeed only 153 4580 movements were cased up in watches that were sold to the public. Just 153. There were not any 4580 movements created separately to the ones submitted to the Neuchatel Observatory for testing and certification.
Some of these movements found their way into Astronomical Observatory Chronometers, and the remaining ones into the Grand Seiko 4580-7000 and 4580-7010 VFA’s. Su Jia Xian recently updated his article on Seiko’s history in the Swiss chronometer trials of the 1960’s with an image of a 4580 movement in an Astronomical Observatory Chronometer.
It can be hard to spot the movement marking on the 4520’s and 4580’s unless you know where to look – it’s on the movement base plate underneath the balance. Here’s a macro shot showing the 4580 marking on my 4580-7010 VFA –
What is interesting about this is that with at least some of the 4580 movements ending up in the Astronomical Observatory Chronometer, it means the absolute upper cap on the number of 4580 VFA’s in existance is less than 150. No wonder they are so hard to find!
It would be great to find out what the split was regarding where the 4580 movements ended up, but what is certain is that one, or possibly both, of the two 4580 VFA variants – the 4580-7000 and the 4580-7010 – is, or are, rarer than then famed Astronomical Observatory Chronometer (*** see end of article if you want to split hairs on the maths!).
And whilst you let that fact sink in, feel free to enjoy the movement of my 4580-7010 in all its Very Fine Adjusted glory in the image below.
As per usual, I recommend you use the top-right icon to go full screen, and then zoom in and pan around to see all the detail.
(*** OK – strictly speaking, it would require 3 examples of the 4580 movement to have been used in the Astronomical Observatory Chronometers in order to guarantee that at least one, possibly both, of the 4580 VFA’s were rarer than the AOC. That would make it 76 AOC’s, and 150 VFA’s in total – if split evenly, that would make 75 of each, if unevenly, then one of them would have a maximum of 74 examples.)