Mention high-end Seiko, and relative newcomers to Seiko will assert Grand Seiko as the be-all end-all, but experienced Seiko hands will always mention King Seiko – like this full-serviced 1973 King Seiko 5625-7113 automatic chronometer here – in the same breath.  Seiko phased out the King Seiko in the 1970’s, virtually ensuring the Grand Seiko would remain more famous.
 
The 5625’s contoured case is pure "Grammar of Design" - the 5625 example here is also a chronometer model, with chronometer certification.  Seiko's Grammar of Design was implemented in Grand Seiko and King Seiko lines from 1967 onwards, making these watches instantly recognizable as status symbols in the hierarchical Japanese business world of the 1960s and 1970s.   In fact, King Seiko's were - and are - held in high regard in Japan, and often gifted by Japanese corporations as awards for decades of service within them.  We love watches like this, and each has a special and usually unique story to tell.
 
But now for some King Seiko history - in 1959, Seiko split up their Suwa subsidiary into two separate entities—Suwa Seikosha and Daini Seikosha—to promote friendly competition and product development within the company, with both operating separately under the idea this would incite good-natured one-upmanship to produce better watches.
 
Well…it worked.
 
That same year, Daini Seikosha hired a young designer by the name of Taro Tanaka, the man who would in the early 1960's create a set of design principles that he called “The Grammar of Design.”   In 1962, Tanaka noticed Swiss watches "sparkled brilliantly" and realized the design of high-end Seiko watches could be radically improved through the implementation of "flat and conical surfaces perfectly smooth and free of distortion."  
 
Tanaka’s rules would go on to fundamentally change Seiko’s design language.  All surfaces and angles of the case, dial, indices and hands had to be flat and geometrically perfect to best reflect light.  Following this aesthetic, the bezels were to be simple two-dimensional faceted curves.  And third, no visual distortion from any angle was allowed, and all cases and dials had to be mirror-finished.  In “A Journey in Time - The Remarkable Story of Seiko,” Tanaka’s approach to the new style is described as follows:

“He started by creating cases and dials that had a perfectly flat surface, with two-dimensional curves on the bezel as a secondary feature.  Three-dimensional curves were not used, as a general rule.  He also decided that all distortion should be eliminated from the dial, too, so that it could be finished with a mirror surface.  This formed the basis for the new Seiko style.”
 
This King Seiko comes on a vintage stainless-steel Maruman bracelet, and with a nylon strap, rugged travel case, and springbar tool.