The Expedition from Boldr is the brand’s self-styled “daily beater.” It has the dial of a field watch inside a dual-crown case with an internal timing bezel. The Expedition II saw a more angular case but with a similar dial layout. The Enigmath update to the series is more than just a new colorway. It brings a new dial style and additional functionality with a slide rule bezel.

Often recognizable by its busy markings on a contrasting-colored, internal, rotating chapter ring, the slide rule bezel is mainly associated with the Breitling Navitimer but also with more affordable watches such as my own Citizen Nighthawk. I only tend to use the second crown on that watch to nudge the rotating bezel back into place. Both crowns on the Boldr Expedition screw down. Thankfully, this nullifies the need to reset regularly.

Boldr Expedition Enigmath lineup

Three gorgeous fumé dials

Aside from the slide rule bezel, the most eye-catching element of these three new watches is the fumé dial. Although most noticeable on the blue and green variants, the effect is strong enough to add some retro appeal to the black dial, too. The inner sections of the dials feature lumed Arabic numerals at the even hours, simple stick markers elsewhere, and a triangle with two dots at 12. The frame handset is in keeping with the simple but legible layout and has plenty of Super-LumiNova applied.

Surrounding the fumé dial is the sloped, fixed part of the slide rule. The transition between the brighter and desaturated center areas to the black backdrop of this inner scale is successfully done, particularly on the colorful green and blue versions. As with any watch with this kind of bezel, things will get busier as you approach the perimeter. What I like most about the Expedition Engimath dials is how the whole tone of the watch changes during that journey.

Boldr has chosen three colorways and aliases that are in keeping with the Expedition theme. Boldr labels the blue dial as “Coconino” after the blue lakes of the Coconino Forest Reserve in Arizona. The biodiversity hotspot of Sri Lanka’s tropical Sinharaja Forest Reserve lends its name to the green dial. Lastly, the black dial is named “Schwarzwald” after the Black Forest in southern Germany.

Boldr Expedition Enigmath Coconico

The Enigmath slide rule adds complexity

Presumably, “Enigmath” is a portmanteau of “enigma” and “math.” The slide rule bezel provides a tool for multiplication, division, speed/time/distance calculations, fuel consumption, ascent and descent rates, and conversions. Thankfully, Boldr includes a handy guide to bezel usage with the watch and a standalone slide rule. This may either be for fun or practice if your eyes sometimes struggle with the smallest text.

Boldr Expedition Enigmath Sinharaja pocket shot

A captivating case

With abundant information displayed on the dial, it’s easy and perhaps necessary for it to be housed in a simple and unobtrusive case. While perhaps reasonably traditional in shape, there are still some nice and interesting touches. First, the case “wings” (which are not large or prominent enough to draw parallels with another more famous watch) make for a more attractive silhouette. On the left-hand side of the 41mm case, the protrusion acts to break up the surface of the case wall and disguise any thickness. On the right-hand side, it acts as a modest crown guard. At almost 13mm thick, the Expedition Enigmath can’t claim to be thin. However, in profile, the thickness is nicely shared between the main case, screw-in case back, fixed external bezel, and a lofty chamfered sapphire crystal.

Tool watches are often sand(or bead-)blasted. The matte finish exudes toughness. I love the rarer combination of sandblasted surfaces and subtle polished facets that Boldr has used here. Like the visual elegance that the fumé effect brings to the dial, the slender polished chamfers bring the same to the case.

The mathematical theme continues on the watch’s reverse. You’ll find a logarithmic spiral among the markings on the crystal, obfuscating the rather plain Miyota 9039 beneath. I’m a fan of the Miyota 9000 series of automatic movements, especially in this price bracket. They offer efficient winding, a smooth sweep of the seconds hand at eight beats per second (28,800 per hour), reasonable accuracy, and a decent power reserve. The 9039 caliber that Boldr has used here is the no-date variant from that family. So, in addition to a date window being missing from the dial, there is no extra crown position for it or a date wheel hidden inside.

Canvas straps for a rugged outdoor watch

Each of the three colorways comes with a matching canvas strap. An extra US$139 will also get you a bracelet for the Expedition series, but the watch is still nice without it. Canvas straps tend to look better as they age, but the holes for the pin buckle can easily stretch and fray. I like the steel eyelets that Boldr uses in the canvas here as they should help the strap last even longer. My wrist also appreciates the leather backing of the strap, especially compared to the roughness of the floating keeper. Over the week I’ve spent with these watches, that has caused a little discomfort.

Boldr Expedition Enigmath Schwarzland wrist shot on bracelet

Final thoughts on the Boldr Expedition Enigmath

I’m one of those people who were never taught at school how to use a slide rule or log tables but also didn’t grow up expecting to carry a pocket calculator at all times. As a result, I don’t know how to feel about this extra functionality. I don’t think it’s aimed at me. But I also don’t know exactly who it is aimed at. In a world where mechanical timepieces compete with ubiquitous electronic devices, I accept that there’s more than a little hypocrisy in saying, “My phone does that.”

Boldr has produced a very smart-looking watch that benefits visually from the slide rule, even if I need more convincing of its broader usefulness. Please let me know in the comments if you would use the slide rule more than I have! The Expedition Enigmath is now available for US$599. For more information on the Expedition series, head to the official Boldr website.

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Watch specifications

Expedition Enigmath (Coconico, Sinharaja, and Schwarzland)
Fumé blue (Coconico), green (Sinharaja), or black (Schwarzland) with painted Super-LumiNova indices
Case Material
Stainless steel with sandblasted finish and polished accents
Case Dimensions
41mm (diameter) × 47.5mm (lug-to-lug) × 12.8mm (thickness)
Sapphire with antireflective coating
Case Back
Sandblasted stainless steel with transparent display, screw-in
Miyota 9039 — automatic and hand winding, 28,800vph frequency, 42-hour power reserve, 24 jewels, hacking seconds
Water Resistance
200m (20 ATM)
Canvas (20mm width) in dial-matching color with steel eyelits and leather backing. Stainless steel three-row bracelet also available separately for US$139.
Time (hours, minutes, central seconds) and slide rule bezel