Apparently Seiya blogged recently about the 4S as part of the Seiko mechanical renaissance recently in April this year and I recently read it.
Given my very personal interest in the Seiko 4S movement, I have to re-post his entry here for reference and sharing.
His post can be found here.
For reference purposes, I’m copying the text here as well.
(p.5-9, GS9 “Grand Seiko Magazine / Grand Seiko Nine” TWO, March 2015)
Seiko formed an in-house mechanical watch project team due to the
positive response received from the 6810 UTD series.
But no engineer with experience in mechanical caliber design was
available in a company.
So, the new caliber, 4S35 was decided to manufacture based on the old
52 caliber, which was produced 20 years ago.
The 52 caliber prided itself on precision of the 1970’s Chronometer standard.
At last, 200,000 4S calibers were produced. Seiko understood it was
too many. However, manufacturing new caliber costs a lot. Seiko had to
make 200, 000 calibers.
The first watch fitted with the 4S was on sale at the end of 1992.
It was SCVK001 (4S35-8000) with 4S35 caliber.
Mechanical watches became the focus of attention in the media.
This boosted Grand Seiko’s mechanical type revival.
Tanaka wanted to create new Grand Seiko with new high-end caliber. But
because there were too many 4S caliber surplus, company didn’t want to
develop new caliber.
As Seiko had to keep to use 4S calibers, they made mechanical watches
like “Credor Chronometers GBAY992”, “KING SEIKO 2000 repro model”, Laurel, and SUS with 4S calibers.
Grand Seiko’s mechanical type revival
Some years later, Seiko began to produce new Grand Seiko with new
mechanical caliber. It was 1996.
A young engineer, Jujo Kouichiro tried to fine-tune 4S calibers for new Grand
Seiko first. But he soon understood it was impossible. Because Grand
Seiko needs more precision accuracy.
Each and every retired technical expert was interviewed in order to
form the new movement.
Many test products were developed by utilizing 3D CAD computer
technology. The precision and structure of the test products were
redone over and over again by ”Ohira Akira”, allowing the completely new movement to be
completed in just 2 short years.
(Please search ”Ohira Akira” by Google)
Personal thoughts after reading this article
1) 4S was revived without the intention to be a temporary stand in for mid tier watches (i.e. for the 6r which was eventually introduced to power mid tier Seikos), nor as a potential movement for the modern GS. It was simply chosen as a result of it boosting the best balance between reasonably good accuracy and manufacturing costs among the movements that Seiko created so far.
It was probably too costly an experiment for Seiko to design and introduce a new mid-high end movement at the start of the mechanical renaissance. Hence Seiko decided to produce the 4S and see how the mechanical watch renaissance will develop from there. Remember this was in the late 1980s / early 1990s.
I also believe that Seiko already had a base mechanical movement to power the low end watches, i.e. 7000 series, but did not find them fit for mid-high tier range of watches that Seiko planned to introduce.
2) 4S was evaluated for its potential to drive the modern day GS, however it did not make the cut. As such, it is indeed inferior to the modern day 8L/9S movements, as also shared to me by a watch technician working in Seiko Thailand.
3) The prime reason for 4S lasting as long as it did (1992-2013/4) and having so many variants (13!) as I mentioned in my original post, was due to the fact that Seiko already produced 200,000 of it! This was more than what Seiko intended.
4) Nevertheless (IMHO), 4S provides the best balance of history, accuracy, variety among all the Seiko movements to date and it deserves a place among Seiko’s honor roll.