Within the world of vintage Seiko, Grand Seiko – distinguished by the “GS” on dial/crown and gold medallion on its caseback, like on this serviced 1969 Grand Seiko 6146-8000 Hi-Beat cross-hair dial dress watch here, on a vintage Seiko stainless-steel bracelet – inhabits the top of the food chain, simple as that. 
 
Grand Seiko – with 51 different models – were simply the most painstakingly designed and exquisite watches made by Seiko, produced by both the Dani and Suwa factories.
 
The Hi-Beat 61GS series - Seiko's very first Hi-Beat Grand Seiko, mind you - started production in 1967, full of Grammar of Design awesomeness.  Sales of the GS 6146 continued until 1974 - nearly the end of the vintage Grand Seiko era in 1975, a self-inflicted fatality of the quartz crisis.  The high-beat credentials of the 61GS are entirely authentic - these GS movements run at 36000 beats per hour or, to put it another way, 10 beats per second or 5 Hz.
 
The 61GS was the second generation of Grand Seiko automatic, following the rather short-lived 62GS that dominated from 1966/1967 to circa 1968 (the 62GS was preceded by the Seikomatic 62 Chronometers in 1966 that were identical in all but branding).
 
Speaking of Grammar of Design, in the early 1960s, Seiko hired a young designer by the name of Taro Tanaka, who created a set of design principles 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."
 
This "Grammar of Design" was implemented in Grand Seiko and King Seiko lines from 1967 and made these lines instantly recognizable as status symbols in the hierarchical Japanese business world of the 1960s and 1970s.
 
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.”
 
Make no mistake, the GS marked, and still marks, the very best Seiko has to offer, easily on par with the vast majority of what Switzerland has to offer by way of competition.  And the 4520 represents one of the highest achievements of Grand Seiko – namely, creating one of the best watches on the planet.  Period.
 
This Grand Seiko comes on a vintage stainless-steel Seiko bracelet, and with leather strap, rugged travel case, and springbar tool.