Let’s set the stage with a dose of shameless bragging and personal sharing: in the past six years on Mainspring and elsewhere I’ve done hands-on reviews of hundreds of tool watches, mostly field, dive, and exploration watches typically under the $1,000 USD price tag and of military flavor. Why? Because this is the type of horology that speaks to my core with the greatest intensity. Why? Because for many years during my childhood and teenagehood my dream was to join the French Special Forces. Why? Because I wanted to become a certain type of man—one who anonymously puts his life on the line to protect others, who is mentally and physically strong, who plays by the rules and embodies a precise set of values (the Stoic cardinal values of courage, wisdom, temperance and justice) and who, simply put, does the right thing for the right reason. In other words, an ideal version of a man which has mostly gone instinct in many Western societies. This review is not, however, a treaty on manhood…I think. 

I evidently didn’t join the French Special Forces because I was told by those I trusted most that I wasn’t mentally and physically fit for it. I regret landing too much of an ear to the words of others and to not listen to myself a bit more. I missed my ticket on the dream career but I can sort of catch up with a small part of it—the bit about being a certain type of man—by way of horology and the study of specific watches. But since this is a watch review and not a dissertation on what it means to be a dude in 2026, I will focus on the watch as I usually do but not before taking a last detour: many of us wear timekeeping devices to express our personality and/or as talismans to inspire us to become someone different, generally better, than we are today. It’s part fake-it-until-you-make-it and part genuinely feeling inspired to step into a new role by way of wearing a specific type of watch. Perhaps this is lame but it is true for most people that I know, regardless of what drives them to do so. 

Thus today we’re going to study the story of three exceptionally brave men through the multipurpose, utilitarian, ultra legible and tough-as-nails MKII Hellion-BAKU and it promises to be a wild ride. 

Specifications 

If you’ve swung by Mainspring before and read one or all of my reviews on Bill Yao’s timepieces—the MKII Fulcrum 39, Tornek-Rayville Type 7B ‘BlakJak,” and Tornek-Rayville CISO M38—then you know and understand that Bill specializes, by way of meticously designed and solidly built tool watches, in telling specific stories about the military which most of us are unaware of. And the more time passes, the more interested he is in recounting the stories of the bravest of men who served during the largest and deadliest conflicts of the 20th century and who proved to be made of a specific type of courage and resolve which I personally feel inspired by. The story of the Hellion-BAKU is that of three members of a U.S. Underwater Demolition Team (UDT), Black, MacMahon, and Roeder, which operated in the Pacific during World War II and were Killed in Action. In partnership with the nonprofit organization Project Recover, MKII’s team partakes in search and recovery missions to better understand what happened to these three men. 

The UDT units were the precursors to the U.S. Navy Seals and their job was reconnaissance and underwater demolition of natural or man-made obstacles in preparation for amphibious landings. Black, MacMahon, and Roeder were part of UDT-10 who launched under the cover of night from the USS Burrfish submarine in August 1944 on a mission to clear the Palaus and Yap islands beaches. UTD divers wore what is commonly referred to USN BUSHIPS “Canteen” watches in the likes of the Elgin and Hamilton 18W8’s of World War II, so named after their ginormous screw-down crown attached to the case by way of a tiny metal chain. UTD divers were time-only watches equipped with water-sealed cases, legible and luminous dials, and a robust build. (Professional dive watches with rotating bezels and crown-guards didn’t see the light of day until the mid 1950s.) For the Hellion-BAKU, MKII started from its Cruxible collection of World War II-era inspired field/pilot watches, the Hellion-Cruxible and Type A-11-Cruxible, which it redesigned and re-spec'ed. 

Simply put, the BAKU has the appearance of a field watch however built to perform extremely well in wet and dry environments of the intense and not-so-intense nature. First, it comes with a contemporary-sized fully-brushed stainless steel case measuring 39mm in diameter, 48.5mm lug-to-lug, 13.55mm thick, and coming with a 20mm lug width and drilled lugs. (The aforementioned 18W8’s measured 32mm in diameter.) The massive and ultra-grippy 8mm screw-down crown is paired with a decorated screw-down case-back for 100 meters of water resistance—I appreciate the fully brushed treatment of the crown to perfectly stick to the military theme. Inside the case beats the rock solid TMI (Seiko) NH38 caliber (3Hz/41 hours of power reserve) regulated in-house in three positions, outside of it we find a double-domed sapphire crystal with several layers of inner anti-reflective coating, and below it, generous applications of green-glowing Arclite SuperLuminova on the hands, printed Arabic numerals and dots flanking them. A true tool watch. 

Design 

Whilst the design of the MKII Hellion-BAKU is based on that of previous models from the brand, and nods to historical and period-correct canteen dive watches from the times Black, MacMahon, and Roeder operated in, it is also to me the three-dimensional representation of the essence which was infused into and leaked out of the most iconic military watches since the 1940s, whether you’re looking at field, pilot, or dive watches. In other words, it is legible, discreet, and functional, thus fashioned into the most effective time-telling wristworn instrument it could be. Furthermore, the BAKU comes across as being the perfect modern tool watch regardless of who you are, where you are, and what you do, as it is a sort of amalgam of numerous versions of utilitarian timekeeping devices I’ve had the pleasure of studying in the past six years, both in terms of dimensions and aesthetics. Thus it could be anybody’s sole activity watch (a noun I heard recently to describe tool watches which I’m going to steal) to do about anything. 

The stainless steel chassis of the MKII is a thing of beauty as it comes with an elongated top-down profile with lugs that stretch right above my wristbones. (The latter measures 6.50”/16.5cm.) The fully-brushed treatment gently tones down its larger-than-usual dimensions for a time-only 100 meter depth-rating tool watch (which I didn’t know would become my new ideal dimensions for such a device) whilst underpinning its decidedly utilitarian nature. Seen from above the case demonstrates a fine example of radial brushing on the upper lug surfaces and fixed bezel, the latter which slopes down and then cliffs towards the mid-case. From the side, another fine example of brushing, this time in a horizontal fashion, accentuates—or marks I should say—the 48.5mm lug-to-lug distance in a way which gives the case an extra dose of purposefulness and which finishes in the equally pragmatic hook-shaped drilled lugs which angle back down towards the wrist. Unsurprisingly, the 8mm crown is glorious in its dimensions, grip, and character. 

Speaking of glory, the dial is also a thing of beauty and the best representation of the legendary legibility the best tool watches have ever been endowed with since times almost immemorial. First on account of its near perfect monochromatic scheme where the classic black-on-white combo was subtly enhanced by the gray tones of the hour and minute hands, rendered this way to nod to the USS Burrfish’s camouflage: World War II American submarines spent most of their time on the surface, thus their upper sides were painted gray to blend in with the sky and their lower ones black to match the color of the deep ocean. To further enhance the dial’s legibility, the bases of both hands were painted black as well the majority of the seconds hand except its lumed tip and fish-spear shaped counter-balance*. The superlative hands are then paired with large Arabic numerals fully made of luminous compound, supported by piercing lumed dots vertically doubled at the twelve, and an effective minute track and blacked-out dial literature.  

*According to MKII’s website, the sweep seconds hand’s asymmetrical triangle counterweight references Project Recover’s logo which symbolizes the vertical stabilizer of the aircraft at the heart of their origin story and folded flag presented to the families of the fallen; representative of recovery and repatriation.

The Heart of the Matter

Looking through the reviews of MKII and Tornek-Rayville watches I’ve published on Mainspring and elsewhere in the past few years, and going through the motions of analyzing Bill Yao’s work again with the Hellion-BAKU, I feel humbled to be able to type so many words about his horological creations because they are all endowed with a double personality, a double meaning if you will, which I have never encountered before. On the first hand, the BAKU is, as all the other ones are, a formidable military-infused tool watch whose generous specifications are equally matched by its superlative legibility and powerful purpose-driven nature. On the second hand, the BAKU is a personalized physical and mechanical representation of the brand’s mission to tell compelling stories about the best examples of bravery in men the U.S. Military has ever been graced with. The Hellion-BAKU is thus the epitome of the perfect tool watch distilled to its best essence, with which we can live purposeful and brave lives, and through which we can be reminded of a certain specimen of men who did the ultimate sacrifice. 

Conclusion

At the end of the day, you would buy the MKII Hellion-BAKU either because you care about the inspiration which drove the brand to create it and who with (Project Recover,) or because you’re searching for an excellent tool watch, or both. Regardless of what brought you here today and whatever happens after that you’ve read another one of my long-ass reviews, you would have learned a bit more about a brand which does things differently and who works with people who too care to tell compelling stories about the bravest of men. And if you were to pull the trigger on the BAKU, you will only set your bank account back $649 USD which is a fair price to pay for how good of a watch it is. For this price you get the watch shipped on a wonderful Haveston M-1944C nylon strap which perfectly matches this timepiece and a sizable donation the brand makes to the nonprofit organization for each sale. 

If you are into good stories about great people, please check out our profile story on Brock Stevens (@deepsee.edc on Instagram) who runs MKII and Tornek-Rayville’s marketing. 

Thanks for reading.