The 4500 family was introduced in 1968 to replace Daini's 4400 calibre. It appeared in the King Seiko 45KS and Grand Seiko 45GS models. Thanks to the "Hi-Beat" accuracy of the 4500 calibre, the 4420 was no longer needed. The date function featured an "instant change" mechanism.
In 1969, Seiko introduced V.F.A. ("Very Fine Adjusted") versions of the 45GS, with monthly precision of +- 1 minute.
- 4520A - GS standard official approval, No date
- 4522A - GS standard official approval, Date
- 4580 - V.F.A., Date
- 4520A - Astronomical Observatory Chronometer official approval, No date
- King Seiki: Special vs. Superior Chronometer
- History of Grand Seiko
- Seiko's Affinity To Hi-Beat Movement