IWC Portugieser Chronograph Ceratanium

IWC Schaffhausen has released the Portugieser Chronograph Ceratanium, officially designated as Reference IW371631 within the current catalog. This release introduces a strictly monochromatic, matte black execution to a model historically characterized by highly contrasting marine chronometer dials and traditional stainless steel or precious metal cases. The Portugieser line traces its origins to the late 1930s, when two Portuguese merchants requested wristwatches housing large, high-precision pocket watch calibers to ensure maritime navigational accuracy comparable to boxed ship chronometers. This historical mandate established the collection's defining physical traits: expansive dial diameters, ultra-thin bezels, and highly legible Arabic numerals designed for instant recognition in adverse conditions. The modern iteration of the Portugieser Chronograph emerged in 1998, establishing a distinct vertical subdial layout that has remained structurally unchanged for over two decades of continuous production. By rendering this traditional layout entirely in dark grey and black tones, the manufacturer shifts the context of the watch from a formal maritime instrument to a high-contrast tactical chronograph. The production of the Reference IW371631 is strictly capped at a limited run of 1,500 individual pieces globally. This low production volume reflects the complex, multi-stage manufacturing processes required for the proprietary case material rather than a simple artificial scarcity model.

The implementation of Ceratanium in this specific reference marks a significant departure from standard case construction methodologies utilized in previous Portugieser iterations. Previous chronographs in this family relied heavily on highly polished surfaces to emphasize the stepped bezel profile and the downward curve of the lugs. In contrast, the Ceratanium alloy yields a uniformly matte, light-absorbing finish that visually reduces the perceived mass of the 41-millimeter case. This design strategy relies entirely on variations in surface texture rather than color contrast to maintain the required legibility of the dial and the readout of the chronograph registers. By eliminating reflective surfaces across the case architecture, the primary handset, and the dial appliqués, the watch forces the wearer to read the time through subtle shadows cast by the elevated metallic numerals against the flat dial base. This monolithic approach represents a structural reinterpretation of the manufacturer's established design language, utilizing advanced material engineering to update a traditional horological format without altering its fundamental geometric proportions.

The Case and Dial

The case measures exactly 41 millimeters in diameter with an overall height of 13 millimeters, maintaining the standard dimensions of the modern Reference 3716 generation chronographs. The primary case components, including the main mid-case, the knurled winding crown, and the pump-style chronograph pushers, are manufactured entirely from Ceratanium. This proprietary material begins as a specialized titanium alloy that is CNC-machined to the precise final tolerances required for the case components. Following the initial machining phase, the components are fired in a high-temperature kiln under strictly controlled atmospheric conditions. During this thermal treatment process, oxygen diffuses directly into the surface of the titanium, inducing a phase transition that converts the exterior of the metal into a hard ceramic structure. This ceramization process yields a surface hardness highly resistant to impact scratches while retaining the underlying structural integrity, high tensile strength, and low overall mass of standard titanium. Unlike traditional Physical Vapor Deposition or Diamond-Like Carbon coatings, which are applied as secondary layers and remain susceptible to flaking or chipping upon hard impacts, the dark metallic finish of Ceratanium is completely integral to the component itself. The case architecture features a very thin bezel framing a convex synthetic sapphire crystal treated with an anti-reflective coating on both the interior and exterior surfaces to minimize light refraction and glare. The complete case assembly provides a baseline water resistance rating of 3 Bar, a standard specification for non-diving chronographs that protects the internal movement from ambient atmospheric moisture and light splashes but strictly precludes any form of submersion.

The dial operates on a strict tone-on-tone methodology, utilizing a matte black base layer engineered to absorb ambient light and reduce surface reflections. To ensure readability without the use of luminous chemical compounds or high-contrast white paint, the manufacturer utilizes polished black appliqués for the primary Arabic numerals and the perimeter minute indices. These individual appliqués are mechanically mounted to the brass dial base, creating subtle physical elevations that catch directional light and cast hard micro-shadows against the matte background layer. The local time is indicated by a set of black, leaf-shaped feuille hands, which are stamped from metal blanks and pressed into their final curvature before receiving their dark surface treatment. The chronograph layout features two vertically aligned, recessed subdials: a 30-minute totalizer positioned at the 12 o'clock position and a running small seconds indicator situated at the 6 o'clock position. Both subdials are finished with concentric azurage, a traditional horological snailing technique consisting of tightly spaced circular grooves that break up the flat texture of the main dial and provide rapid visual distinction for the secondary readouts. Framing the entire dial assembly is a steeply angled inner flange printed with a precise quarter-second scale. This outer track allows the wearer to take accurate elapsed time readings that correspond precisely with the 4 Hertz operating frequency of the internal escapement mechanism.

The Movement

Powering the Reference IW371631 is the proprietary Calibre 69355, an automatic, self-winding mechanical chronograph movement that remains fully visible through the synthetic sapphire exhibition caseback. The Calibre 69355 is a core component of the 69000-calibre family, engineered internally by the manufacturer to replace the outsourced, cam-actuated chronograph movements previously utilized in the older Reference 3714 generation. This specific caliber relies on a traditional column-wheel mechanism to govern the starting, stopping, and resetting phases of the chronograph functions. The column wheel is a precisely machined vertical cylinder with vertical pillars; when a pusher is engaged by the wearer, the operating levers fall into or ride up onto these pillars to engage the lateral clutch of the chronograph geartrain. This specific architecture provides a distinct, uniform tactile resistance when actuating the pump pushers and drastically reduces the initial forward jump of the central seconds hand that is commonly associated with standard cam-and-lever systems. The escapement operates at a frequency of 28,800 vibrations per hour, equivalent to 4 Hertz, ensuring the central chronograph seconds hand advances in precise quarter-second increments that align directly with the corresponding scale printed on the dial flange. The movement is constructed from 205 individual components and utilizes 27 synthetic ruby jewels to minimize mechanical friction at critical gear train pivot points. The gear train also incorporates a hacking seconds mechanism, which mechanically halts the balance wheel when the winding crown is pulled to the outermost position, facilitating exact time synchronization against an external reference signal.

The kinetic energy required to maintain the 46-hour power reserve is generated by an automatic double-pawl winding system linked directly to the oscillating weight. This bidirectional winding architecture utilizes two rocking pawls that continuously pull on a central winding wheel regardless of which direction the rotor travels, maximizing the kinetic energy harvested from the wearer's daily wrist movements and ensuring the mainspring remains near peak torque. The finishing techniques applied to the Calibre 69355 are executed to standard high-end horological specifications and remain fully visible through the rear sapphire aperture. The large, skeletonized rotor dominates the upper visual plane and features a central recess housing a gold-toned medallion deeply engraved with the Probus Scafusia seal, indicating the manufacturer's strict internal quality standard. Beneath the oscillating weight, the upper movement bridges are decorated with straight, uniform Côtes de Genève striping, while the visible sections of the main baseplate are finished with overlapping circular graining, commonly referred to as perlage in the industry. The structural components are secured by highly polished steel screw heads set deep into recessed countersinks. The perimeter of the Ceratanium caseback framing the sapphire crystal features deep, machine-cut engravings denoting the manufacturer's name, the collection designation, the 3 Bar water resistance specification, and the text ONE OF 1500, designating the watch's status as a limited production model without assigning individual sequential serial numbers to specific units.

The Strap

The watch is secured to the wrist using a specialized black rubber strap designed specifically to integrate with the exact dimensions of the 41-millimeter case. The strap features a lug width of 20 millimeters at the case attachment points and tapers down sharply to an 18-millimeter width at the closure mechanism. This specific tapering geometry reduces the overall bulk of the material beneath the wearer's wrist, improving the ergonomics of the watch during extended periods of wear.

The exterior surface of the vulcanized rubber is molded with a dense, repeating square pattern that closely mimics the visual texture of woven textiles or traditional tropic-style diving straps. This textured surface breaks up the monolithic appearance of the flat rubber and aligns visually with the matte, light-absorbing properties of the Ceratanium case. The strap is fastened using a standard pin buckle, which is also machined entirely from Ceratanium to ensure complete material and color uniformity across all exterior touchpoints of the watch assembly.

Pricing and Availability

The IWC Portugieser Chronograph Ceratanium, officially designated as Reference IW371631, is restricted to a total global production volume of exactly 1,500 units. The manufacturer distributes this limited reference directly through its network of official physical boutiques as well as its primary corporate e-commerce platform. The retail pricing reflects the proprietary material science integrated into the case construction and the proprietary internal mechanics.

Orders placed through the digital e-commerce channel include complimentary standard delivery logistics, with specific routing handled by secure carriers to either residential or professional addresses within a typical window of three to five business days. Clients utilizing the direct purchasing model also have access to the brand's concierge shopping service for detailed technical consultations over the phone. Furthermore, the manufacturer offers digital augmented reality applications allowing prospective buyers to perform virtual sizing assessments on their own wrists prior to final acquisition.

Technical Specifications

Case: Ceratanium, 41mm diameter, 13mm height, convex sapphire crystal with dual anti-reflective coating, sapphire display back, 3 Bar water resistance

Movement: IWC Calibre 69355, automatic self-winding, 46-hour power reserve, 28,800 vph (4 Hz), 205 components, 27 jewels, column-wheel chronograph

Dial: Matte black with black applied Arabic numerals, black feuille hands, azurage subdials, printed quarter-second scale

Strap: Black textured rubber strap with square pattern, 20mm lug width tapering to 18mm, Ceratanium pin buckle

Price: Available upon request via IWC distribution channels

Reference Number: IW371631

Notes: Limited global production of 1,500 pieces