Welcome back to another Seiko-flavored edition of Historical Horology. Last week’s dive into the Seiko Monster proved popular, which makes sense. The Monster is a popular entry-level diver, and it is also one that John and I have recommended quite a bit. While that last article really was more of a look at how the watch and it’s movement are put together, this week we do have a more historical look at the Seiko Tuna. It’s not a particular deep history, considering that the watch was introduced in 1975, but it is a history nonetheless.


The Seiko Tuna Prospex (short for Professional Specification) actually got its start (on the drawing board, at least) in 1968, when Ikuo Tokunaga and his engineers realized their current dive watches were not up to the task of saturation diving. Something was needed that could withstand that environment and have its crystal popping off. Seeing what we see today, it might be tempting to think they simply slapped in a helium escape valve and called it a day. Then again, if that was all they did, we probably would not be talking about it today.


No, the Seiko Tuna ended up with a one-piece case (made from titanium), a specially-shaped gasket, and a host of other innovation that led to 20+ patents being granted. Also of interest (to those who pay attention to movement specs), the first Seiko Tuna had a movement that was beating at 36,000 BPH (aka 10 Hz). When you consider the era the watch was introduced, it becomes all the more stark just how big the case was when the watch was introduced. Even by today’s standards, 51mm is still a big watch. Subsequent models (which were ultimately quartz-driven) did shrink a touch, but they were still big dive watches, replete with the signature shroud.


Over the years, there have been various stylistic changes, and movements, but we do still see a quartz-driven Seiko Tuna in the lineup. This makes sense, as if you are truly using this as a dive tool, the accuracy quartz provides is the important factor. There was also a smaller version of the Tuna (which had only a 300m WR rating, and a caseback) introduced, making basically three major divisions within the lineup. For more details on all three, and the changes they’ve gone through over the years, check out this excellent article over at Monochrome.

All images courtesy of Monochrome

3 thoughts on “Historical Horology – The Seiko Tuna”

Leave a Reply