*This is a working item, but the operating time has not been measured.

■ Condition of scratches and dirt
Crystal: Minor
Case back: Minor
Bezel: Minor
Strap: New aftermarket part
Calendar:

Background of King Seiko and the "56KS" series

In the 1960s, Seiko established the crown brands "Grand Seiko" and "King Seiko" to produce mechanical watches with higher precision and quality in Japan. They also engaged in development competition between multiple factories within the company (especially Suwa and Daini).

One of the main lineages of King Seiko is the "56KS" series, which was manufactured from around 1968 to 1975.

Typically, the 56 series was handled by Suwa Seikosha, and the 56KS was positioned as a high-precision model made by Suwa.

The "56KS" series includes models with date mechanisms (with date display) and non-date models (without calendar).

Starting from Scratch with Wristwatches

Overview and positioning of the 5621-7020 model
The "5621-7020" is considered one of the non-date (no calendar, automatic winding, high-beat) models in the 56KS series.
Below are the main features and known information about this model.

Item | Content
------- | --------
Caliber | Cal. 5621 (56 series automatic winding, non-date specification)
Vibration frequency (high-beat) | Described as 28,800 vibrations per hour (= 8 vibrations/second) in listing specifications.
Manufacturing period | Multiple units confirmed to be manufactured in 1971, with auction listings stating "manufactured in September 1971".
Case design | A refined round case typical of the 56KS series, with a design that eliminates unnecessary ornamentation. As a high-beat specification, it emphasizes precision and stability.
Rarity and current market price | It is available at a relatively affordable price range, but prices vary depending on the condition and originality. Watch media has introduced it as being available for around "$400-$600". However, there are also examples of successful bids in the 30,000-40,000 yen range in Japanese auctions.

Special notes and precautions

This model has no date display, so some sellers list this as an advantage, stating that there is no risk of calendar malfunction, which is a common issue with the 56 series.

There are also descriptions mentioning that the case back originally had the "KS" logo and gold medallion decoration.

The 56 series King Seiko was a lineage that pursued "design, finishing, and precision" within the context of quality pursuit comparable to Grand Seiko. In particular, the philosophy of "Grammar of Design" (design aesthetics, geometric composition, and polishing surface design) was adopted from the late 1960s, emphasizing a design style with sharp edges and contrasting mirror-finished surfaces.

However, there is less abundant documentation for the mass-produced models within the 56 series, and systematic lineage charts for specific reference numbers (such as 5621-7020) do not appear to be widely compiled.