Citizen Tsuno Bullhead AN3660-73X Review: The Full-Lume Retro Chronograph

In the expansive archives of Japanese watchmaking, the 1970s stand out as an era of fearless experimentation. It was a decade defined by funky case shapes, vibrant colors, and radical departures from traditional horological norms. Among the most celebrated designs to emerge from this period was the "Bullhead" chronograph—a watch architecture that moved the crown and pushers from the side of the case to the top, resembling the horns of a bull.

Today, as the watch industry experiences a massive resurgence of interest in vintage-inspired designs, Citizen has reached into its rich heritage to resurrect this iconic silhouette. The result is the Citizen Tsuno Chrono AN3660-73X. Released as part of the brand's "Record Label Playground Edition," this timepiece is not just a lazy reissue; it is a vibrant, modern reinterpretation of a motorsport classic.

With its historically accurate 38mm case, highly reliable quartz movement, and a show-stopping full-lume dial, the AN3660-73X offers enthusiasts a chance to own a piece of avant-garde 1970s design without the fragility or maintenance costs associated with vintage mechanical chronographs. This comprehensive review explores the history, the mechanics, and the undeniable charm of Citizen's modern Bullhead.

The Origins of the "Tsuno" Bullhead: A 1970s Legend

To fully appreciate the design language of the Citizen AN3660-73X, we must travel back to 1973. During this time, the global watch industry was locked in a fierce race to perfect the automatic chronograph. While Swiss brands like Heuer, Breitling, and Zenith were making headlines, Japanese giants Seiko and Citizen were quietly producing some of the most robust and innovative chronograph calibers in the world.

The 1973 Citizen Challenge Timer

In 1973, Citizen released the Challenge Timer, powered by the legendary Caliber 8110A. This was an engineering marvel: a high-beat (28,800 vph), automatic chronograph with a flyback function, a column wheel, and vertical clutch engagement. But what truly made the Challenge Timer famous was its case design.

Citizen released a version of the Challenge Timer where the movement was rotated 90 degrees counter-clockwise inside the case. This placed the winding crown and the two chronograph pushers at the top of the watch (the 12 o'clock position) rather than the traditional 3 o'clock position. In Japan, collectors immediately nicknamed the watch "Tsuno Chrono," with "Tsuno" translating to "horn." In Western markets, it became universally known as the "Bullhead."

The Ergonomics of the Bullhead Design

The Bullhead design was not merely an aesthetic gimmick; it was born out of functional necessity for motorsport racing.

First, placing the pushers at the top of the case mimics the layout of a traditional handheld mechanical stopwatch. This allows the wearer to operate the chronograph with their index fingers while gripping the case with their thumb, providing a much more intuitive and tactile timing experience.

Secondly, traditional chronographs with pushers at 3 o'clock can often dig uncomfortably into the back of the wearer's hand, especially when the wrist is bent backward (such as when gripping a steering wheel). The Bullhead configuration completely eliminates this ergonomic issue, making it the ultimate driver's watch.

The AN3660-73X Design Language: Retro-Futurism Realized

With the Citizen AN3660-73X, the brand has masterfully captured the spirit of the original 1973 Challenge Timer while updating the materials and finishes for the modern collector. It is a watch that looks simultaneously nostalgic and futuristic.

The 38mm Sweet Spot

One of the most commendable decisions Citizen made with this reissue was resisting the urge to upsize the case. In an era where many brands inflate their vintage reissues to 42mm or 44mm to suit perceived modern tastes, Citizen kept the AN3660-73X at a highly authentic 38mm in diameter.

This 38mm dimension is the absolute "sweet spot" for a Bullhead design. Because the pushers and crown protrude from the top of the case, a larger diameter would make the watch wear incredibly long and awkwardly on the wrist. By maintaining the compact 38mm width and a relatively slim thickness of 11.7mm, the watch sits perfectly centered on the wrist. It offers substantial visual presence without sacrificing comfort, making it suitable for a wide variety of wrist sizes.

The Stainless Steel Architecture

The case is constructed from high-quality stainless steel, featuring a beautiful mix of brushed and polished surfaces. The bezel slopes smoothly down toward the spherical mineral crystal, which adds a lovely vintage distortion to the dial when viewed from sharp angles.

The lugs are short and sharply angled downward, ensuring that the bracelet drops straight down to hug the wrist. The pushers at 11 o'clock and 1 o'clock are prominent and offer a satisfying, tactile "click" when engaged, while the crown at 12 o'clock is deeply grooved for easy manipulation.

The Star of the Show: The Full-Lume Playground Dial

While the Bullhead case shape is the foundation of the watch, the dial of the AN3660-73X is its undeniable centerpiece. This specific model is part of the "Record Label Playground Edition," a sub-collection where Citizen's designers are given the freedom to experiment with playful, unconventional color palettes.

The Mint Green Glow

In daylight, the dial presents itself in a striking, pale mint green or teal color. It is a fresh, vibrant hue that immediately sets it apart from standard black or white chronographs. However, the true magic happens when the lights go out.

The entire surface of the mint green dial is heavily coated in luminous paint. This is known as a "full-lume" dial. When transitioning from a bright environment to a dark room, the entire face of the watch glows with an intense, radioactive-looking luminescence. It is a spectacular visual effect that guarantees the watch will be a conversation starter at any evening event.

High-Contrast Legibility

To ensure that the watch remains highly legible against the glowing background, Citizen utilized a high-contrast "panda" style layout. The dial features four deeply recessed, jet-black sub-dials and a black tachymeter rehaut around the outer edge.

• The Sub-dials: The layout consists of a running seconds register at 6 o'clock, a 60-minute chronograph counter at 12 o'clock, a 12-hour chronograph counter at 9 o'clock, and a 24-hour indicator at 3 o'clock.
• The Hands: The main hour and minute hands are polished steel with their own luminous inserts. To inject a dose of 1970s racing flair, the central chronograph seconds hand, as well as the small hands in the chronograph sub-dials, are painted in a vibrant, high-visibility orange.
• The Date Window: A subtle, circular date window is neatly tucked away at the 4:30 position, providing daily utility without disrupting the symmetry of the four sub-dials.

The combination of the glowing green dial, the stark black registers, and the popping orange hands creates a visual dynamic that is incredibly fun, yet highly functional.

The Engine: Citizen Caliber 0510 Quartz Movement

The most significant departure from the original 1973 Challenge Timer is found beneath the solid stainless steel caseback. While the vintage model utilized a mechanical automatic movement, the modern Citizen AN3660-73X is powered by the in-house Caliber 0510 quartz movement.

Why Quartz Makes Sense

For some mechanical purists, the use of a quartz movement in a vintage reissue might seem like a compromise. However, in the context of the "Playground Edition," it is a highly logical and consumer-friendly choice.

Re-engineering a modern, mechanical flyback chronograph movement to fit a Bullhead configuration would have pushed the retail price of this watch well into the thousands of euros. By utilizing the Caliber 0510, Citizen is able to offer the iconic Tsuno design and the spectacular full-lume dial at an incredibly accessible price point (typically under €300).

Furthermore, the quartz movement offers "grab-and-go" convenience. Vintage mechanical chronographs are notoriously expensive to service and delicate to operate. The Caliber 0510, powered by a standard SR927W battery with an approximate 2-year lifespan, is a robust, worry-free engine. It provides an accuracy of ±20 seconds per month, ensuring that your retro timepiece is always perfectly on time.

Chronograph Functionality

Despite being quartz, the Caliber 0510 is a highly capable timing instrument. It can measure elapsed time down to 1/1th of a second, with a maximum capacity of 12 hours. This makes it far more practical for timing long events (like a road trip or a flight) than standard 30-minute or 60-minute chronographs.

Wearability and Everyday Utility

A watch can have the most interesting design in the world, but if it is not comfortable to wear, it will ultimately end up sitting in a drawer. Citizen has ensured that the AN3660-73X is a highly capable daily wearer.

The Milanese-Style Sliding Clasp Bracelet

The watch is fitted with a vintage-inspired stainless steel bracelet. It features a fine-pitch, multi-link design that visually mimics the look of a classic Milanese mesh bracelet, but with the structural rigidity of solid links.

One of the best features of this bracelet is its sliding clasp mechanism. Unlike traditional bracelets that require you to hammer out pins or unscrew links to adjust the size, the sliding clasp allows for infinite, tool-free micro-adjustments. You simply lift the locking mechanism, slide the clasp to your desired position on the bracelet, and lock it back down. This ensures a perfect fit on any wrist size, ranging from 135mm to 200mm.

Water Resistance and Durability

The watch boasts a water resistance rating of 5 ATM (50 meters). While this does not make it a professional dive watch, it is more than sufficient for daily life. It can easily withstand rain, hand-washing, and even light surface swimming or showering. Combined with the tough stainless steel case and the scratch-resistant spherical mineral glass, the AN3660-73X is built to survive the rigors of everyday use.

The Collector's Appeal: A Limited Edition Rarity

In the modern watch market, exclusivity drives desirability. The Citizen Tsuno Chrono AN3660-73X is not a standard production model; it is a Limited Edition restricted to just 4,000 pieces worldwide.

This limited production run, combined with the highly unusual full-lume dial and the beloved Bullhead case shape, makes it an instant collector's item. It appeals to a wide spectrum of enthusiasts: vintage Citizen collectors looking for a modern daily wearer, fans of 1970s motorsport aesthetics, and collectors who simply appreciate bold, unconventional dial designs.

As these 4,000 pieces find their way into private collections, the AN3660-73X is likely to become a highly sought-after reference on the secondary market, much like the original Challenge Timers of the 1970s.

Conclusion: Embrace the Horns at WatchExclusive

The Citizen Tsuno Chrono Bullhead AN3660-73X is a triumph of retro-futuristic design. It proves that a watch does not need a five-figure price tag or a Swiss mechanical caliber to be incredibly fun, historically significant, and visually stunning.

By combining the legendary ergonomics of the 1973 Challenge Timer with the playful, glowing exuberance of the Playground Edition full-lume dial, Citizen has created a timepiece that refuses to be ignored. It is a watch that celebrates the joy of horology—a reminder that sometimes, the best watches are the ones that don't take themselves too seriously.

At WatchExclusive, we are passionate about offering timepieces that tell a unique story. The Citizen AN3660-73X is a rare opportunity to strap a piece of 1970s motorsport history to your wrist, updated with modern reliability and a dial that lights up the night. Due to its strict 4,000-piece global limitation, inventory is highly restricted. We invite you to explore this glowing masterpiece and secure your limited-edition Bullhead today, before it disappears into horological history once again.

References

• BE FORWARD Store. (2026). CITIZEN record label Citizen RECORD LABEL PLAYGROUND Edition AN3660-73X. Retrieved from BE FORWARD.
• Fratello Watches. (2026). Hands-On With The New Quartz Citizen Challenge Timer “Tsuno”. Retrieved from Fratello Watches.
• Heureka.sk. (2026). Citizen AN3660-73X pánske hodinky. Retrieved from Heureka.sk.
• Masters In Time. (2026). Citizen Sport AN3660-73X Bullhead Challenge Timer 'TSUNO' Watch. Retrieved from Masters In Time.
• The Gadgeteer. (2026). Citizen Tsuno Reissue: The Cheapest Bullhead in Years. Retrieved from The Gadgeteer.