The Bremont ALT1-ZT/51 is a retired automatic GMT chronograph that combines a 24-hour second-time-zone display with elapsed-time measurement. Its 43 mm hardened-steel case, 16 mm thickness and inner rotating bezel give it a substantial aviation-and-travel-watch profile. Bremont marks the reference as retired, so its official listing does not establish current reseller availability or a current market price.
What does “ZT” mean on the Bremont ALT1-ZT/51?
Bremont says “Z” stands for “Zulu Time.” The ALT1-ZT/51 is designed to show local time alongside a second time reference: UTC, GMT or Zulu time. These labels are closely related in this use; the 24-hour GMT hand provides the second-time-zone indication, while an inner bi-directional Roto-Click bezel helps set and read it. Bremont’s description is on its official ALT1-ZT/51 product page.
What does the watch do?
The watch brings together a conventional time display, date, GMT hand and chronograph. Bremont lists central hour and minute hands, seconds, a date at 3 o’clock, chronograph counters for seconds, 30 minutes and 12 hours, and a 24-hour GMT hand. The chronograph measures elapsed time; the GMT hand tracks a second time zone on a 24-hour scale.
The inner bezel is operated by the crown at 8 o’clock. For basic chronograph operation, Bremont has a chronograph tutorial that explicitly covers ALT1-ZT.
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- 38mm stainless steel case
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ALT1-ZT/51 specifications
| Specification | Bremont-published detail |
|---|---|
| Movement | Modified automatic BE-54AE chronometer, calibre 13 1/4”’; 25 jewels |
| Frequency | 28,800 beats per hour |
| Power reserve | 42 hours |
| Additional movement details | Glucydur balance, Anachron balance spring, Nivaflex 1 mainspring and decorated Bremont rotor |
| Case | 43 mm hardened stainless steel with Trip-Tick construction and a scratch-resistant DLC-treated case barrel |
| Thickness | 16 mm |
| Lug width | 22 mm |
| Water resistance | 10 ATM / 100 metres |
| Crystal | Double anti-reflective, scratch-resistant sapphire |
| Bezel | Inner bi-directional Roto-Click bezel, operated by the crown at 8 o’clock |
| Dial and hands | Coated nickel hands with Super-LumiNova luminous coating |
| Case back | Stainless steel with an integrated flat crystal and six screws |
| Listed strap configuration | Calf-skin leather strap with deployment buckle; Bremont also lists the reference separately on a steel bracelet |
Bremont describes the movement as a chronometer rated to ISO 3159; its earlier press-release material says C.O.S.C. tested and certified. That is the manufacturer’s model-level description, not confirmation that a certificate accompanies any particular second-hand watch. The technical details and leather-strap configuration also appear in Bremont’s ALT1-ZT/51 press release.
How to assess a retired ALT1-ZT/51
Bremont marks the ALT1-ZT/51 as retired from its catalogue. The official product page does not say whether resellers currently have stock, establish a prevailing resale price, or set out warranty transferability, service costs or original-parts availability. Any purchase decision therefore needs to be based on the specific watch and seller rather than an assumed current retail offer.
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- Confirm the reference and configuration. Bremont lists both a leather-strap version and a separate steel-bracelet listing. Do not infer which one is being offered from the reference name alone.
- Inspect condition and service history. Request clear photographs, a description of wear and damage, and available service records.
- Check included documents carefully. If a seller claims C.O.S.C. certification, verify that the paperwork corresponds to the individual watch being sold.
- Verify accessories and fit. The published lug width is 22 mm, but compatibility of a particular replacement strap or attachment is not established by that measurement alone; confirm fit before buying.
- Evaluate the seller’s evidence. Ask for the exact reference, configuration, condition details and documentation that support the listing.
Is the current Altitude Chronograph GMT the same watch?
No. Bremont’s current US page for the Altitude Chronograph GMT describes a distinct watch with a 42 mm 904L steel case and BC781 movement with a 62-hour power reserve. Those differ from the ALT1-ZT/51’s published 43 mm case and BE-54AE movement with a 42-hour reserve. Bremont’s page does not establish the Altitude as a direct replacement or successor.
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- Movement : ST2502
- Dial diameter : Approx.43mm
- Thickness : Approx.13.5mm
- Strap width: Approx.22mm
- Strap circumference : 19m
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