The 44GS series was developed by Daini Seikosha, based on the movement originally introduced in 1964 with the King Seiko Chronometer (ref. 4420-9990).
Taro Tanaka and the Grammar of Design
Thanks to the contribution of the designer Taro Tanaka, the guidelines of the “Grammar of Design” are introduced, which will define the Grand Seiko style from that moment on.
The model with reference 4420-9000 is the first Grand Seiko to follow the guidelines of Taro Tanaka’s Grammar of Design: flat surfaces and geometrically perfect angles to best reflect light, mirror-polished faceted bezels, no distortion, recognizable cases with original designs.
Ref. 4420-9000 (Diashock)
Movement: 4420
Type: manual
Jewels: 27
Bph: 18.000
Case: stainless steel
In the first version there is the Diashock writing under the Grand Seiko brand at 6 o’clock, which will soon be replaced by the Daini logo visible in the next version, with the same case-movement reference.
Ref. 4420-9000 (Daini logo)
Movement: 4420
Type: manual
Jewels: 27
Bph: 18.000
Case: stainless steel
Version of 4420-9000 with the Daini logo on the dial.
Ref. 4420-9990
Movement: 4420
Type: manual
Jewels: 27
Bph: 18.000
Case: gold cap
It shares the same case-movement reference as the King Seiko from which the 44GS series originated. The King Seiko 4420-9990 was available in stainless steel and gold cap, while the Grand Seiko 4420-9990 appears to have only been produced in the gold cap version.
| Movement | Type | Jewels | Bph | Complications | Technical information |
| 4420B | Manual | 27 | 18.000 | – | Japanese |