Seiko’s first range of truly submersible sports watches came in the form of the Seikomatic 50m SilverWave in 1961, which marked a number of firsts for Seiko – it represented the Japanese company’s first dive watch; their first watch with an inner rotating countdown bezel; their first use of the tsunami wave symbol; and it was their first automatic watch with a screw-down case back.
 
Fast forward to the ever more refined full-serviced 1978 Seiko 6306-8010 Silverwave "Tokyo Theatres Company" automatic diver here, which has lost some of the early diver’s rough edges yet retained all (and then some) of the charm.
 
But why do we call this a "Tokyo Theatres Company" diver?
 
Engraved on the watch's caseback in Kanji Japanese is the phrase, "Award for Continuous Service, 10 Years; Tokyo Theatres Company, Ltd," marking this as a commemorative award to a loyal employee for 10 years of loyal service at the Tokyo Theatres Company.
 
Established in mid-1946, the Tokyo Theatres Company was founded to provide entertainment through movies to a devastated post-World War II Japan.  Tokyo Theatres has kept this mission statement in mind since, and continues to "move forward with its mission of adding color to people's lives by continuing to create a variety of services while changing its business structure to meet the needs of the times, rather than remaining limited to the movie exhibition business."
 
Tokyo Theatres is engaged in the diverse businesses of film entertainment, movie distribution, integrated advertisement, and event planning.  But like many Japanese companies, the Tokyo Theatres Company corporate structure is bizarrely complex. 
 
Tokyo Theatres concentrates its business efforts in three main areas.  First and foremost, its core businesses are video-related (film production and distribution, movie theater management, comprehensive advertising services, and event planning).  It also operates food and beverage businesses (restaurant management – including the yakitori specialty restaurant Kushitori – and food processing and sales).  Finally, it operates real estate businesses (which consists real estate rentals, and the renovation and rental of used apartments).
 
As of late 2024, the company realized ¥17,057 million in FY2023 ($110 million USD) in sales, and remained small in size (at least compared to many Japanese corporations), with nearly 500 employees.
 
As for the Seiko 6306 diver itself?  Between 1965 and 1975, Seiko brilliantly conceived, designed, and produced three generations of classic ISO-certified 150 m divers’ watches, in chronological order - the 62MAS, 6105-8000/9, and the 6105-8010/9.  Then 1976 arrived...
 
That year, Seiko debuted its replacement for its 6105, conceived in two different specifications - one of which was the 6306 for the domestic Japanese Domestic Market and the 6309 for the international market; the JDM variant - the Calibre 6306 - was fitted with a more advanced 21 jewel 6306A movement, with hacking and an English/Kanji Japanese day wheel.
 
The 6306 lived a rather short life in between the 6105 and down-jeweled and less complex 6309, and was produced from 1976 to 1981, when Seiko would favor the 6309 until it too was replaced with the 7002 diver in 1988.  The 6306 calibre was a successful effort by Seiko to improve the 6105 movement, which allowed for greater lifespan, robustness, and ease of maintenance.
 
This Seiko 6306 automatic diver comes on a leather-backed canvas strap, and with nylon strap, rugged travel case, and springbar tool.