The Derby Swissonic tells time with numerals on rotating drums, not conventional hands—and its minutes jump forward as well as its hours. Built around an electromechanical movement associated with the ESA 9176 Dynotron, it is a mid-1970s watch whose unusual display is also its most important buying risk: the drums must work, not just the movement.
How the Derby Swissonic’s jump-minute display works
Instead of hands sweeping around a dial, the Swissonic presents numerals through narrow apertures. Its display is a mechanical arrangement of rotating drums: seconds advance continuously, while the minute display changes in jumps and the hour drum advances hourly. The result resembles a miniature speedometer more than a conventional wristwatch.
Fratello characterizes the display as a plastic “drum-machine” powered by a seven-jewel transistorized electromagnetic module, and associates the movement with the ESA 9176 Dynotron. That is an enthusiast article’s technical description, rather than a manufacturer specification. Fratello’s account describes a small spring in the display train as part of the jump action.
A separate specialist reference explains the mechanism as a battery-energized electromagnetic coil and balance wheel, with an escapement transmitting motion through a rod and gears to the drums. CrazyWatches’ repair and reference page gives that account. Together, these descriptions point to a delicate electromechanical watch—not a modern quartz digital display.
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- 1.316L Stainless Steel Case/Screw Crown/Steel Closed Caseback
- 2. Seagull ST1721 Jump Hour Mechanical Movement
- 3. Sapphire Crystal / Diameter: 34.5MM / Case Thickness : 10.4MM / Lug to Lug =45MM
- 4.Comfortable Rubber Strap /5.Butterfly Clasp
- 5.Band Width: 20MM*18
When it appeared—and what related examples exist
The available accounts place the Derby Swissonic in the mid-1970s, but do not establish one definitive launch date. Fratello says the ESA movement was introduced at the 1974 Basel Fair; the specialist reference dates the watch to around 1975. Related Jaz-branded examples are also described, along with chrome- and gold-plated variants. Those details come from secondary sources, not a primary manufacturer catalogue or specification.
What to check before buying one
For this watch, a running movement is not enough. The display train can fail independently of the apparent motion of the movement, and the sources warn about fragile plastic gears and possible caseback damage.
Rank #2
- 1.316L Stainless Steel Case/Screw Crown/Steel Closed Caseback
- 2. Seagull ST1721 Jump Hour Mechanical Movement
- 3. Sapphire Crystal / Diameter: 34.5MM / Case Thickness : 10.4MM / Lug to Lug =45MM
- 4.Comfortable Rubber Strap /5.Butterfly Clasp
- 5.Band Width: 20MM*18
- Watch the full display advance. Ask to see the seconds, minute drums and hour drum working. Observe it over several minutes to confirm that the minute display actually jumps and that the drums remain aligned and legible.
- Inspect the case and caseback. Look for cracks, damage around the plastic hatch and signs of rough opening or repair. Have a knowledgeable watchmaker assess the case and gearing if you cannot inspect them confidently yourself.
- Ask about service and parts. Request a clear account of repairs, replaced components and whether the display mechanism has been serviced. Because the drum train is delicate, seek a watchmaker familiar with vintage electromechanical watches before committing to a repair-dependent example.
- Verify the battery requirement for that watch. CrazyWatches reports a 357 1.5 V cell for the model and notes that 1.35 V mercury cells are no longer made. Older watches may have been modified, and no manufacturer manual is established here, so have a qualified watchmaker check the individual watch before fitting a battery.
- Compare examples on evidence, not labels. Condition, demonstrated operation, originality of parts and bracelet, case variant and service history are more useful comparison points than a seller’s generic description. Treat a listing’s details as claims about that particular watch.
How it wears and sounds
Fratello author Tomas Rosputinsky describes the case as challenging to wear and notes a lively ticking sound and an audible click as the minute changes. Those are his impressions, not guaranteed traits of every surviving example. The recessed numerals and narrow apertures give the display a distinctive visual effect: the current reading stands out while adjacent digits remain hidden.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the historical price evidence can—and cannot—tell you
A Watch Auction lot for a described Derby Swissonic sold for £240 on 21 October 2020, against an estimate of £250–350. The auction record documents one sale of one example. It is not a current valuation, a representative average, or evidence of today’s availability.
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Rank #3
- 1.316L Stainless Steel Case/Screw Crown/Steel Closed Caseback
- 2. Seagull ST1721 Jump Hour Mechanical Movement
- 3. Sapphire Crystal / Diameter: 34.5MM / Case Thickness : 10.4MM / Lug to Lug =45MM
- 4.Comfortable Rubber Strap /5.Butterfly Clasp
- 5.Band Width: 20MM*18
The cited sources do not establish a verified production total, tested accuracy figure or population-wide failure rate. A specialist source discusses spring-related malfunction, but the available material does not provide a verifiable sample or study from which to estimate how often it occurs.
Quick Recap
Best Value
- Jump Hour
- One Pointer Minutes Hand
- Small Second Hand
- Automatic winding 20 Jewels
- Vintage
Rank #4
- 1.316L Stainless Steel Case/Screw Crown/Steel Closed Caseback
- 2. Seagull ST1721 Jump Hour Mechanical Movement
- 4.Comfortable Genuine Leather Strap with pin buckle
- 6. AR Coated Sapphire Crystal / Diameter: 39MM / Case Thickness : 10.4MM / Lug to Lug =46.8MM
- 7.Band Width: 20MM*18
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