The rivalry between Suwa Seikosha and Daini Seikosha is proof that a little internal pressure can unlock serious creativity. In the 1960s, Daini, or Kameido, was often viewed as the more conservative arm of Seiko, but the rise of the 5 Sports and SpeedTimer lines marked a shift. As competition intensified, so did experimentation, and with it came some of the brand’s most distinctive chronographs. The idea that Daini’s chronographs were inferior to Suwa’s doesn’t hold up, and if anything, Daini was often the bolder of the two.
 
The Seiko Time Sonar Ref. 7015-6010, introduced in 1976, feels like one of the final, fully realized expressions of that chronograph chapter: Inspired by submarine sonar displays, it features a semi-transparent dial that reveals the calendar disk beneath, creating depth and motion rarely seen in vintage chronographs. 
 
Beyond its transparency, the translucent orange dial is carefully composed. Slim white hour markers keep it light, while a black minute track and angled tachymeter ring frame the design with structure. Bold black segments at 3 and 9 o’clock organize the branding and day-date, giving it an instrument-panel feel. White hands with floating black centers remain crisp, and the vivid green chronograph seconds hand cuts across the orange field: If that isn’t sonar in motion, it’s hard to call it anything else. The smoked display case back reveals Daini's proprietary flyback Cal.7015A, something Daini attempted first worldwide. 
 
If you've been following for a while, you might remember they orgiinly come in bracelet like one we sold a while back, and this one is a very rare rubber strap variant which works so well on it. While Seiko revisited the aesthetic of the Time Sonar in 2022 with the Kosuke Kawamura collaboration models Seiko SRPJ41 and Seiko SRPJ43, as well as the recently announced SBSA323, nothing quite matches the originality of the 7015-6010.
 
The watch currently works flawlessly and will be sold as-is. Please let us know if you wish to service it.
 
Ships from Tokyo, Japan.