What makes this model so compelling is the way boldness and meticulousness coexist in just the right balance.
A case distinguished by generously voluminous planes and a dynamic slope that smoothly connects to the case side has an unadorned, decisive form, and its stylish, streamlined silhouette evokes a futuristic mood. The prominently protruding push button iconically expresses the model’s headline function—its built‑in stopwatch.
In contrast to the case’s dynamism, the dial is crafted with a deliberate interplay of density and openness. The comfortable tension between the thick, commanding indexes and the finely detailed minute track stands out, while the distinctive window frame—composed of three facets—feels bold yet meticulously executed, with chamfered corners and an inner slope finished in black. Carefully considered details abound. The green and yellow accent colors within the sub‑dials are restrained in saturation, becoming vivid highlights against the dial’s nearly‑black dark gray.
With generous negative space and obsessively refined micro‑details, this thoughtfully balanced watch harmonizes curves and straight lines to exude a sense of futurism—a design that excites the sophisticated wearer.
The boldly protruding push buttons are iconic, and the streamlined form exudes a futuristic vibe. Simple yet powerful, with no unnecessary elements.
A voluminous side view. The bezel is thin, and the boldly sloped surface smoothly connecting the case side softens the overall volume.
The dial’s linear design features a striking contrast between dynamic indexes and a meticulous minute track.
The boldly constructed window frame is finished with three different surfaces, making the facets stand out for a sharper impression. Details like chamfered edges and meticulous craftsmanship are evident throughout.
Green and yellow accent colors, not overly saturated, add a sophisticated and mature touch to the nearly black dark gray dial.
The case is characterized by bold, open surfaces and dynamic slopes that smoothly connect to the case sides. The dynamic surface composition creates a refreshing, futuristic atmosphere. The boldly protruding, iconic push buttons make the function a distinctive design feature.
The boldly protruding, iconic push buttons make the function a distinctive design feature.
The linear hands feature luminescence for visibility in the dark. The base of the hour and minute hands is black, creating a floating, light impression with just the tips standing out.
ENGINEER'S EYE
A well-fitting chronograph
While it had been considered a design challenge to combine an automatic winding mechanism with chronographs that had traditionally been available only in hand-wound form, once several companies released chronographs in 1969, development also began at CITIZEN.
The hallmark of the “Cal. 8100 Challenge timer,” released in 1972, is its thin construction. By compactly integrating a reverser-type automatic winding mechanism, offsetting the second wheel from the center, and further adopting a vertical-clutch seconds chronograph wheel—already proven in the hand-wound chronograph “Cal. 5700 Record Master”—the movement’s mechanical elements, which tend to cluster near the center, were skillfully dispersed. The result was an outside dimameter of φ27 mm and a thickness of 5.82 mm for the movement.
Leveraging this movement size to the fullest, the Challenge timer offered a lineup spanning a variety of design tastes. Produced not only as a sports watch aimed at young people, many calmer, professional-looking models were also manufactured.