The BALL Roadmaster M Model A pairs an automatic movement with a mechanical gong alarm and a GMT hand that, together with its 24-hour bezel, can be used to track three time zones. BALL describes it as a 333-piece limited edition. Its published dimensions and purchase details differ by market and listing, so the exact reference matters when comparing specifications or checking availability.
What is the BALL Roadmaster M Model A?
BALL Watch Japan announced the Roadmaster M Model A on October 25, 2024, describing it as the company’s first mechanical-alarm model after three years of development. Its Japanese reference is DA9100C-S1J-BKR. BALL’s English product page lists the Roadmaster M Model A (41mm) under reference DA9100C-S1-BKR; the suffixes belong to separate listings and should not be assumed interchangeable. The Japanese announcement said applications would open October 31, 2024, at 9:00, a historical launch schedule rather than a current ordering window. BALL Watch Japan’s announcement and the English product listing identify those market-specific details.
The defining combination is a mechanical alarm and GMT functionality in an automatic watch. BALL’s English listing identifies the movement as caliber RRM7379, while retailer Eye Eye Isuzu lists the Japanese-reference watch with caliber RR7379. Because the naming differs between the manufacturer’s listing and retailer, verify the reference and movement designation for the market listing you are considering.
How the mechanical alarm works
BALL Japan says the movement uses separate mainsprings for timekeeping and the alarm. A single rotor winds the timekeeping spring when it turns in one direction and the alarm spring when it turns in the other. When activated, a hammer strikes a gong; BALL says it developed a longer gong to improve tone and sustain. This is a mechanical striking alarm, rather than an electronic beep.
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The Japanese announcement describes two screw-down crowns with distinct roles:
- 4 o’clock crown: winds the alarm, sets the alarm time, and switches the alarm on or off.
- 2 o’clock crown: handles ordinary winding, GMT adjustment, date adjustment, and time setting.
Retailer Eye Eye Isuzu reports an alarm duration of up to 18 seconds for the Japanese reference. That duration is retailer-reported, not listed on the cited English manufacturer product page. Eye Eye Isuzu’s listing also gives other movement details, including 31 jewels, 28,800 vibrations per hour, and a 45-hour power reserve.
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How the GMT hand and bezel track three time zones
The GMT hand is quick-set, according to BALL’s campaign page, and indicates a second time zone alongside the main time display. The bidirectional 24-hour bezel can be used with that hand to read a third geographic zone. In practical terms, the dial shows local time, the GMT hand can be set to a second zone, and the bezel can be rotated to interpret the GMT hand against another zone’s offset. The bezel’s 24-hour scale distinguishes day from night as well as indicating the hour.
BALL’s English product listing calls the feature a luminous three-time-zone indication. The manufacturer’s description establishes the intended use of the GMT hand and bezel; it is not an independent assessment of legibility or ease of use. BALL’s campaign page presents the GMT hand as quick-set and explains the three-zone concept.
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Manufacturer-listed specifications
The following figures come from BALL’s English product listing for reference DA9100C-S1-BKR, identified there as the 41 mm version. They are manufacturer specifications, not independent test results.
| Specification | BALL English listing |
|---|---|
| Movement | Automatic caliber RRM7379 |
| Edition | Limited to 333 pieces |
| Functions | Mechanical alarm; three-time-zone indication |
| Case | 904L stainless steel; 41 mm diameter; 15.2 mm height |
| Crystal and case back | Anti-reflective sapphire crystal; transparent sapphire case back |
| Bezel | Ceramic 24-hour bezel |
| Water resistance | 100 m/330 ft |
| Shock resistance | 5,000 G |
| Anti-magnetism | 4,800 A/m |
| Luminous material | 29 micro gas tubes |
| Approximate weight and lug width | 170 g; 20 mm |
These resistance and construction figures describe BALL’s stated specifications; the cited product page does not establish independent testing of this individual watch.
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Why dimensions and weight differ between listings
BALL Watch Japan’s 2024 announcement for reference DA9100C-S1J-BKR gives a 43.5 mm bezel diameter, 15.2 mm thickness, and approximate weight of 189 g. It also describes a 904L stainless-steel case, a bidirectional ceramic-top bezel, anti-reflective sapphire crystal, and a stainless-steel bracelet with folding buckle. By comparison, the English product page for DA9100C-S1-BKR gives a 41 mm case diameter and approximate weight of 170 g.
A case diameter and bezel diameter can refer to different measurement conventions; the pages do not fully reconcile either the size figures or the weight difference. Treat each set as specific to its source and reference rather than combining them into one definitive measurement. If fit or heft is important, confirm the exact regional reference and how the retailer measures the watch.
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Price and availability depend on market
BALL Watch Japan’s October 25, 2024 announcement listed a suggested retail price of ¥880,000 including tax for its Japanese-market announcement. BALL’s English listing has displayed US$6,899 with estimated six-month availability, while other official page captures showed different prices and lead-time estimates. Those online displays are market- and time-specific, not a universal current price or delivery promise. Check the live listing for your region and the precise reference before ordering.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
