What is a Seiko Tuna?

Seiko Tuna

The Seiko Tuna is the watch that solidified Seiko’s reputation as a developer of specialty, precision time pieces. The Tuna is also the first divers watch to utilize both a monocoque titanium case and quartz movement. This is a watch designed not for looks, but as a tool for saturation divers. To be clear, saturation diving isn’t the same as recreational diving. Saturation divers must stay submerged for hours at a time, and is considered a rather dangerous occupation. That being said, they required tools with the ability to withstand being in the same environment without breaking. Thus, the Seiko Tuna was born.

Ikuo Tokunaga

According to the U.S. Bureau of Labor Statistics, commercial divers spend their work day submerged, repairing structures, performing underwater welding tasks, installing structures, and so on. In order to perform such duties, both diver and equipment must be able to handle the stresses of the environment. In 1968, a commercial saturation diver sent a letter to the Seiko offices in Japan regarding the quality of their diving time pieces. Seiko designed and developed their first diving watch in 1965. They were what they were, and left much to be desired. The diver was assigned to work on the oil fields near Japan, and found that the Seiko diving watches he and his fellow divers used were just not cutting it. He related his experiences with the watches, stating they were consistently breaking down while submerged, and was curious about any solutions to this issue.

Enter Ikuo Tokunaga. One can consider Tokunaga as a dedicated and devoted master of his craft. During his decades long career, Tokunaga has been a leader in the development of a great variety of high precision, specialty watches such as divers, pilots, railway and adventure watches. He also was the chairman of the International Organization for Standardization, Back in 1970, Tokunaga was one of Seiko’s best engineers. When he was assigned to find a solution to the dive watch problem, he saw this as a challenge to be won, and spent the next 5 years searching for a workable solution. Finally, in 1975 Tokunaga designed and developed the Seiko Tuna. In point of fact, Tokunaga himself presented a Seiko Tuno to the commercial diver from from Kure City, in Hiroshima, whose 1968 letter inspired the change. The diver tried it out, and gave it his seal of approval.

Why “Tuna” ?

By this time, some of you may be wondering, “Why Tuna?” Nicknames you see, are no stranger to Seiko watch enthusiasts. Their watches have always inspired fans to grant them their own pet names, such as Monster, Turtle, Mohawk, Spork, Shogun and a few more by their fans. In this case, we’re turning our attention to the Seiko Tuna, and how it got that nickname. The Seiko Tuna is a rather large watch, measuring 48mm in diameter. As it’s a specialty time piece, fashion takes a huge step backward when it comes to this watch, and that’s where the nickname “Tuna” comes in. When enthusiasts saw the watch being worn, it reminded them of a can of tuna strapped to the wrist. It’s the large, bulky bezel shroud, which protects the case, that makes this watch resemble a can of tuna.

Seiko Tuna Movements

The movement or caliber, is what powers the hands and all other functions required to keep time and are either mechanical or quartz. One can tell the difference between the two as mechanical movements require winding, and the quartz movements need batteries. The Seiko Tuna time pieces include four basic movements, which include: 6159B, 7C46, 7549A, and 5M23. For example, the Grandfather Tuna represents the first generation Tuna, and had a 6159B movement. 7549A and 7C46 movements are found in the Golden Tuna, 7C46 in the Darth Tuna, and the 5M23 can be found in the Baby Tuna unit.

Grandfather Tuna: The First Generation

As stated, the Seiko Tuna was born of the need for professional divers to be able to have a watch which could withstand the pressure of being submerged for long periods of time. Due to the efforts of Tokunaga and team, the Seiko 6159-7010 saw the light of day. Known as “Grandfather Tuna”, this large specialty watch measured 51mm and was the first to have a titanium case and a depth rating of 600 meters. Marketed to the public in 1975, Seiko continued this model until 1979.

The Seiko Golden Tuna

The Seiko 7549 Golden Tuna came with a depth rating of 1000 meters. When the Golden Tuna was presented to the public, fans noticed its gold titanium inner case, so bestowed the nickname of “Gold Tuna” upon it. If you ever have a chance to watch Roger Moore in “For Your Eyes Only”, you may notice that he’s got Bond wearing a Seiko Golden Tuna watch. What makes the Seiko Golden Tuna 7549 stand out is the introduction of the quartz movement to the diving watch in 1978.

Seiko Darth Tuna

Enthusiasts of the Seiko’s all black, DLC coated titanium SBBN011 Tuna christened it the “Darth Tuna”. Also known as the “Hockey Puck”, it had a 1000 meter depth rating. a flat sapphire crystal, 49mm black titanium shroud, Quartz Seiko 7C46 7 Jewel movement, and attached to the wrist via a polyurethane strap.

Save The Ocean Special Edition

Seiko realizes that the environment where its Tuna watches are used are places to be cherished. That’s why it created the “Save the Ocean” special edition time pieces. Here, Seiko designers craft special edition Tuna’s and donates a percentage of the profits from these watches to chosen environmental organizations. A good example are those models which center around the frozen waters of Antarctica. In this case, the 43mm Seiko Prospex Baby Tuna and the 50mm Monster, SRPG57K1 and SRPG59K1 respectively.

Final Thoughts

Since function bests fashion, we can see that the overall design and construction of the Tuna has remained basically the same since Tokunaga introduced the first generation in 1975. Watches such as the Seiko Tuna are worthless unless they can perform the tasks asked of them. With the exception of special edition models, such as the “Save the Ocean” time pieces, the exterior of the Tuna has basically remained unchanged. As they are professional time pieces, and seen as tools of the trade, they have remained relatively affordable throughout the years.

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