King Seiko 5625-7121 Hi-Beat – March 1973 – Cal. 5625, 25 Jewels, 28,800 A/h – Serviced 2026

King Seiko is the name under which Seiko’s Daini factory competed against its own Grand Seiko for decades – and, for the most part, remained on par. This example of the 56KS series offered here is the final and technically most mature development stage of this line: Hi-Beat automatic with 28,800 vibrations per hour, 25 jewels, and date, serviced in Japan with workshop documentation.

The Two Kingdoms

In the 1960s and 1970s, Seiko maintained two competing watch factories: Suwa Seikosha and Daini Seikosha. Both developed independently, both built top-tier models, and both competed internally against each other – a rivalry that propelled Seiko to the global forefront during that era. Grand Seiko and King Seiko are the visible result of this competition.

King Seiko was never the weaker line, but rather the alternative one: the same standards for accuracy and craftsmanship, a different design approach, and noticeably more accessible in price. For collectors today, this is exactly what makes the line interesting – you receive the manufacturing quality of Seiko’s top tier without paying Grand Seiko price levels.

The Caliber 5625

The 56 platform is Seiko’s most mature automatic construction of that era. The caliber 5625 operates with 25 jewels and 28,800 vibrations per hour – the Hi-Beat frequency explicitly stated on the dial. The higher frequency makes the movement less sensitive to positional changes and shocks and allows for finer adjustment; it is the reason why Hi-Beat movements are still considered the more sophisticated construction principle today.

This is complemented by automatic winding, a date display, and an overall height of just 10 millimeters, which is typical for the 56 family – remarkable for an automatic movement of this caliber.

The case back is stamped SEIKO · KS · WATER RESISTANT · STAINLESS STEEL · 5625-7121 with the serial number 334691, dating the watch to March 1973.

Serviced

The watch was fully and professionally serviced in Japan in the summer of 2026. With a Hi-Beat movement, this is not a luxury, but a necessity: the higher frequency places greater demands on oils and bearing tolerances, and an unserviced 28,800-vph movement wears out faster than one with a slower beat rate.

Design and Character

The silver dial is finely satin-finished and features applied, multi-faceted indices whose edges refract light sharply – a hallmark of Seiko’s top lines and the reason these dials literally sparkle in cross-light. The "SEIKO / AUTOMATIC" signature is at 12 o'clock, the KS logo with "HI-BEAT" at 6 o'clock. The framed date window is at 3 o'clock.

The stainless steel case measures 36.7 mm excluding the crown, with a 41.1 mm lug-to-lug and a height of only 10 mm. The angular, sharply defined case flanks are the true mark of quality: they are created by the elaborate Zaratsu polishing that Seiko uses in its top lines, which even sixty years later reveals whether a case has ever been over-polished. Weighing 49 grams on the black leather strap, the watch wears light and formal.

Condition

The dial and case are in good condition with only minor signs of wear; the crystal is clear without any major scratches. The original crown with the KS logo is installed, and the edges of the watch remain sharp.

Technical Specifications

• Brand: King Seiko
• Reference: 5625-7121
• Caliber: Seiko 5625
• Movement: Automatic
• Jewels: 25 Jewels
• Vibrations: 28,800 A/h (Hi-Beat)
• Functions: Hours, minutes, sweep seconds, date
• Manufacturer: Daini Seikosha
• Case material: Stainless steel
• Diameter excluding crown: 36.7 mm
• Lug-to-lug: 41.1 mm
• Height: 10 mm
• Lug width: 18 mm
• Weight including strap: 49 g
• Serial number: 334691
• Dating: March 1973
• Service: Fully serviced in Japan in summer 2026
• Strap: Black leather strap
• Origin: Japan

For whom?

For collectors looking for the Seiko top tier of the early 1970s who consciously prefer King Seiko over Grand Seiko. For anyone wanting a Hi-Beat movement on their wrist – the design that is still considered the more sophisticated one today. And for buyers who value documented service more than any promise.

Warranty (used)

This is a used item. The limitation period for claims for defects (statutory warranty) is 12 months from delivery.

Note

As this is a pre-owned watch, water resistance cannot be guaranteed. To protect the movement, the watch should not come into contact with water or moisture.