Description
Citizen Hisonic tuning fork wristwatch
MADE IN JAPAN
The Citizen Legacy: A Pioneer of Precision
Founded in 1918, Citizen is now one of the largest watch and movement groups in the world. The Japanese brand is known for its highly accurate and reliable Eco-Drive solar-powered watches. The Citizen group owns Bulova, Alpina, Frederique Constant, and Arnold & Son, as well as movement manufacturers Miyota and La Joux-Perret.
About the Hisonic Line
In 1971, Citizen entered a licensing partnership with the American maker Bulova to bring “tuning fork” watch technology to Japan for the first time. Bulova had pioneered the technology in 1960 with the Accutron, using an electrically driven tuning fork resonator — vibrating at 360 Hz — in place of a conventional balance wheel, driving the hands through a tiny index wheel and pawl. Citizen manufactured the movements themselves under license, badging the resulting watches “Hisonic.”
The Hisonic line launched with the three-hand caliber 3701, followed by the day-date 3702, and later the 3721 fitted to this watch — a refined three-hand-only movement without the date complication. All shared the same architecture as Bulova’s own 218/2182 calibers, and Citizen priced the line as a genuine premium offering: Hisonic models sold for 38,000 to 60,000 yen in 1973, well above an ordinary mechanical watch of the day. Around a million were made before production ended in 1977, when quartz crystal timekeeping made the tuning fork’s famous “hum” obsolete almost overnight.
About This Watch
This example is a Citizen Hisonic from January 1975, reference 3721-375076 Y, serial 50100522, powered by Citizen’s caliber 3721A tuning fork movement (15 jewels) — Citizen’s licensed version of the Bulova Accutron mechanism. Rather than a balance wheel or quartz crystal, the movement drives an electrically excited tuning fork that hums at 360Hz, indexing the hands through a tiny pawl-and-wheel mechanism for the smooth sweeping seconds hand tuning fork watches are known for. It carries a teal sunburst dial signed “CITIZEN TUNING FORK HISONIC,” a clean three-hand layout with no date complication, on a vintage stainless steel mesh bracelet.
Technical Specifications
- Brand: Citizen
- Line: Hisonic
- Reference Number: 3721-375076 Y
- Movement: Citizen caliber 3721A tuning fork (15 jewels), licensed from Bulova’s Accutron mechanism
- Serial Number: 50100522
- Production Date: January 1975
- Case Material: Stainless steel
- Case Diameter: ~38mm
- Dial: Teal sunburst, applied baton markers, three-hand with no date complication
- Crystal: Acrylic crystal
- Case-back: Screw-down stainless steel, engraved with reference and serial numbers
- Country of Manufacture: Japan
Condition Report
The dial and indices are clean and glossy with strong, even teal color and no notable fading or staining. The case shows honest, light wear consistent with its age – a few fine surface marks on the lugs and case sides, with no dents or heavy over-polishing evident. The stainless case-back is engraved with the reference and serial numbers, fully legible, with light surface brassing typical of a case this age. The stainless steel mesh bracelet is present and functions correctly; the clasp is unsigned, so while the bracelet is period-correct, we can’t confirm it’s the factory-original bracelet for this specific watch (see sizing in the product photos).
Watch went through a recent service by a professional watch technician and keeps good time.
Comes complete with vintage steel bracelet*.
(*)Note: Stock bracelets are often shortened by previous owners and may not fit you(see bracelet size in the product images). We recommend adding a new Citizen lug width matched leather strap with your order.
This watch ships from 🇺🇦Ukraine with tracking number
Why Collectors Want This Watch Today
Tuning fork watches are a genuine curiosity on today’s vintage market — a technology that existed for barely a decade before quartz replaced it, and one most collectors have read about but rarely held. This Hisonic pairs that mechanical rarity with a striking teal sunburst dial, a bolder color than the silver and champagne dials most commonly seen on 1970s Citizens. Hold it to your ear and you can hear the tuning fork’s characteristic hum, and watch the seconds hand sweep smoothly rather than tick — something no ordinary mechanical or quartz watch can replicate. It’s a fitting piece for anyone who wants a slice of horological history that looks as distinctive as it sounds.
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Citizen lug width matched leather straps: 18mm -19mm - 20mm
About the watch factory
The Spirit of Innovation: The Citizen Legacy
Founded in 1918 with the mission of creating timepieces that are “Citizens” of the world, the Citizen Watch Company has spent over a century redefining the boundaries of horology. From its origins as the Shokosha Watch Research Institute, the brand has remained steadfast in its philosophy: “Better Starts Now.” This belief—that it is always possible to make something better—transformed a local Japanese workshop into a global powerhouse of precision and craft. By controlling the entire manufacturing process in-house, from the individual components to the final assembly, Citizen ensures an uncompromising standard of quality that few manufacturers on earth can match.
What truly sets Citizen apart is its relentless pursuit of pioneering technology paired with environmental consciousness. The brand made history by introducing the world’s first light-powered watch, the Eco-Drive, which eliminated the need for battery replacements and forever changed the industry’s approach to sustainability. Beyond its eco-friendly milestones, Citizen’s history is decorated with “world firsts,” including the first professional diving watch with an electronic depth sensor and the most accurate satellite-synchronized timekeeping systems. When you wear a Citizen, you aren’t just wearing a watch; you are wearing a piece of history engineered for the future.
Why Choose Citizen?
- In-House Excellence: Every movement is manufactured vertically within their own Japanese facilities.
- Eco-Drive Technology: Powered by any light source, ensuring your watch never stops and never needs a battery.
- Heritage of Firsts: A century-long track record of technical breakthroughs in durability and precision.
