|Brand:||Daini Seikosha, Grand Seiko, Seiko|
|© Seiko Cal. 4520 was used in Daini Seikosha's Grand Seiko models||Complications:||Date, Instant Date Change|
|Hands:||Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Window at 3:00|
|Distinguishing Technical Characteristics|
|Production: 1968 – 1972|
Cal. 4522A was a hand-winding Hi-Beat movement with date produced by Daini Seikosha from 1968 through 1972 for their Grand Seiko watches. It was an upgrade over Cal. 4420 thanks to the 10 Hz (36,000 A/h) speed and the addition of a date complication. The closely-related Cal. 4502 was used in King Seiko models and was tuned and finished to a slightly lower standard. The similar Cal. 4520A lacked the date mechanism.
Seiko 45 Stream Overview
Throughout the 1960s, Seiko had two internal operations competing for watchmaking supremacy. Suwa Seikosha, formed in 1959, focused on high-end men’s watches and originated the Grand Seiko line. Daini Seikosha, the historic watchmaking operation for Hattori Seikosha, developed the alternate King Seiko line before creating the famous Grand Seiko Style with the 44GS of 1967.
In 1968, both Suwa and Daini produced a Hi-Beat movement fit for a Grand Seiko watch. The Suwa 6100 stream was an automatic while the Daini 4500 was hand-wound. Both were used in Grand Seiko models until the decline of mechanical watches in that line around 1975.
The Daini Seikosha 4500 stream replaced the respected but slow-beating 4400 stream in King Seiko and Grand Seiko models. The move from 5 Hz to 10 Hz had been a singular technical challenge for Daini, both from a design and metallurgical standpoint. But the movement featured other technical advances as well, including an “instant” date change mechanism.
Compared to the Suwa automatic movement, Daini’s 4500 stream was more elegant in design, with a classic hand-winding look and full balance bridge. It was also notably thinner, giving Daini’s watches a desirable design differentiator.
|Cal. 4500||1968-1972||King Seiko||No|
|Cal. 4502||1968-1973||King Seiko||Yes|
|Cal. 4520A||1968-1974||Grand Seiko||No||Some tuned for Observatory Chronometer use|
|Cal. 4522A||1968-1972||Grand Seiko||Yes|
|Cal. 4580 VFA||1969-1973||Grand Seiko||No||Very Fine Adjustment, limited production|