Summarized and translated the article, “A way to rebirth of Seiko’s mechanical watches”
(p.5-9, GS9 "Grand Seiko Magazine / Grand Seiko Nine" TWO, March 2015)
Production of the new 4S caliber
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)