Seiko "Yellow Fin" Baby Tuna - SRP639K1 

September 13, 2018

Aside from the case and functionality, buyers of timepieces are aesthetically attracted by the overall color scheme of a watch. Such is the case for Seiko when they decided to release their popular baby tuna model in black, white and yellow and Seikoholics have coined it the "Yellow Fin" baby tuna.

The Seiko SRP639K1 is a popular and affordable choice for people who love the Tuna-line. Lets take a look into the "Yellow Fin" and find out if it will be one of Seiko's modern day classics.

Look and Feel

One of Seiko's classic case designs has been the "Tuna". From our research, it stemmed because the watch case resembled a tuna can because of its massive circular shroud.


Because of its unique looks and appeal, Seiko released into somewhat a smaller version of the original Tuna and dressed it up with colors that would suit a modern-day diver.

The original tuna's had huge case shrouds that would protect the watch head for saturation diving. With the shroud, most tuna's case sizes would range from 47-51mm. Seiko released the Yellow Fin baby tuna into a smaller and more manageable 45mm case (with shroud). 


The stainless steel shroud, paired with a black bezel with white and yellow markings gave the SRP639K1 its unique character. The addition of the yellow-lined minute hand closed the deal for it to become an instant looker for a diver.

Lug width is at 22mm which gives its owners multiple strap options. It comes out of the box with a trademark black curved-end rubber strap which is quite comfortable on the wrist.


We've met a few Seiko lovers who slapped on a stainless steel bracelet (Google: Super Engineer bracelet) that made the whole watch facade jump at you more. Nato's/Zulu's would also work as you can see with the attached pics. 

Seiko SRP639K1 on Super Engineer Bracelet (Source: Here)

The Yellow Fin Baby Tuna in a military-style green Zulu strap


Given the price point for the Yellow Fin Baby Tuna, we've already expected it to have the ever-so-dependable 4R36 Automatic movement. Wish list? We would have wanted to see a 6R series movement housed in it though.


You would find the Seiko Yellow Fin Baby Tuna ranging from $300 - $700 USD all over the internet (depending on which part of the world you buy from). If you can get them at the lower part of the price range mentioned above, then that would be one heck of a deal! 


The Seiko Yellow Fin Baby Tuna is an attractive watch with its clean yet striking color combinations. However, not everyone would appreciate the shroud and case size.


WIS (watch idiot savant's) would have a hard time appreciating it especially if the put side to side with the original Seiko Tuna's. 


If I do see another person wearing this, it tells me the following:

  • Not afraid to wear larger watches

  • Loves sporty and casual wear (especially the color yellow)

  • Appreciates the Seiko Tuna and Saturation diving scene

Watch Daddy Rating


  • Attractive color scheme

  • Stainless steel shroud shows its diving heritage

  • Affordable (depending on your continent)


  • Wears rather large and sits high on the wrists

  • Won't fit under a dress shirt

Worth Considering

Watch Daddy Picks

Seiko "Yellow Fin" Baby Tuna - SRP639K1 

  • Stainless Steel Shroud

  • Seiko automatic movement (Caliber 4R36)

  • LumiBrite hands and markers

  • Water resistant to 200 meters (660 feet)

  • 45mm case width

  • Black rubber strap

Watch Daddy Alternatives

Seiko Black Baby Tuna - SRP637

  • Stainless Steel Shroud

  • Seiko automatic movement (Caliber 4R36)

  • LumiBrite hands and markers

  • Water resistant to 200 meters (660 feet)

  • 45mm case width

  • Stainless Steel Bracelet

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