The Alpina Seastrong Diver Heritage, reference AL-525S4H6, pairs a design Alpina says is inspired by 1960s professional divers with a manufacturer-rated 300 m water resistance. Its headline details include a 42 mm steel case, automatic movement, internal rotating bezel and 21 mm lug width. Whether it suits you depends on your preferred case size and bezel operation, and on checking the exact regional listing and strap fit.
What is the Alpina Seastrong Diver Heritage?
Alpina identifies this watch as the Diver 300 Heritage, reference AL-525S4H6. The company describes it as a reissue inspired by its 1960s professional-diver design, but the product pages do not name a specific original reference, original release year or designer. The historical claim is therefore best understood as design inspiration, not proof that this is a reproduction of a particular vintage model. Alpina US product page; Alpina UK product page.
What are the specifications?
| Specification | Manufacturer-published detail |
|---|---|
| Reference | AL-525S4H6, as listed by Alpina US and UK |
| Movement | Automatic AL-525. Alpina’s UK page says it is based on the SW200, with 26 jewels and 28,800 alternations per hour. |
| Power reserve | 38 hours, stated on Alpina’s UK page. |
| Case | Stainless steel; 42 mm diameter and 12.3 mm thick, according to Alpina’s US page. |
| Water resistance | 300 m / 30 ATM, as stated on Alpina’s US and UK product pages. |
| Crystal | Anti-reflective sapphire on the US page; the UK page describes a box-style sapphire crystal. |
| Functions and controls | Date; internal 60-minute rotating bezel; screw-down crown, according to Alpina. |
| Lug width | 21 mm, as listed by Alpina. |
These are manufacturer-published specifications, not independent measurements. Regional page copy differs in some descriptions, so use the full reference and the specific regional listing when comparing offers. The movement and reserve figures above come from Alpina’s UK page: Seastrong Diver Heritage.
How big is the watch?
Alpina lists a 42 mm case diameter and 12.3 mm thickness on its US product page. Those figures give a useful starting point, but they do not establish how the watch will sit on a particular wrist. If possible, compare those dimensions with a watch you already find comfortable; consider the case thickness as well as diameter when judging how it may fit beneath a cuff.
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- The Seastrong Heritage model is inspired by the 1960’s professional diver design, a beautiful re-issue of this historic model. This timepiece features an automatic movement with a 60-minute internal rotating bezel. It also has a textured rubber strap, vintage white and black dial, screw down crown and an engraved caseback to protect the movement from everyday elements.
- 300M water resistant with uni-directional turning 60m diving bezel
- AL-525 Caliber - Automatic Self-wind Movement, 26 jewels, 38 Hours Power Reserve
- 42mm Case Diameter with Polished Stainless Steel Case
- Scratch Resistant Sapphire Crystal
How does the internal bezel work?
The bezel tracks up to 60 minutes, but it is internal rather than an external ring. Alpina’s manual says it is bidirectional and cannot be moved unless the crown is unscrewed. Follow the manual’s operating instructions before using it; remember to secure the crown afterward. This is a different interaction from turning an exposed external bezel, so consider which style you prefer. Alpina 2024 user manual.
Is it suitable for diving?
Alpina rates the watch to 300 m / 30 ATM and specifies a screw-down crown. That rating is the manufacturer’s stated water resistance; it is not an independent test report or a guarantee of the condition of an individual watch. Anyone intending to dive with a particular example should follow Alpina’s manual and have the watch’s condition and water resistance checked by a qualified watch service provider, especially after opening the case or if its service history is unknown.
Rank #2
- The Alpina Seastrong Diver 300 Heritage is the ultimate automatic dive watch, water resistant to 300M and measuring immersion time up to 60 minutes.
- The 42mm stainless steel case features a green sunray dial with luminous silver colored hands.
- The stainless steel caseback is engraved with Alpinas beloved Alps and a trident, and is anchored to a green rubber strap that is sand, sea salt- and corrosion-resistant.
- Equipped with the AL-520 automatic caliber with 38hr power reserve.
What strap fits the Alpina Diver 300 Heritage?
The listed lug width is 21 mm, and Alpina’s UK page shows compatible 21 mm strap options. Width alone does not verify that every strap will attach correctly or suit this exact reference. Check the strap’s fit and attachment details against AL-525S4H6 before ordering, and confirm current stock with the seller. Alpina UK product page.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What should you check before buying?
- Confirm the reference: Match the listing to AL-525S4H6 rather than relying on the broader Seastrong or Heritage name.
- Check the regional specifications: Alpina’s pages do not use identical wording for every detail; read the page for the market and variant being sold.
- Compare fit dimensions: Use the stated 42 mm diameter, 12.3 mm thickness and 21 mm lug width as checks against your preferences and any replacement strap.
- Understand the bezel: The internal bezel is crown-operated, not an external rotating ring.
- Verify price and availability directly: Alpina’s US page displayed $1,995 and its UK page displayed £1,595 on 2026-10-08. These are regional manufacturer-listed prices observed on that date, not a like-for-like currency comparison, and may change.
These specifications establish what Alpina claims, but they do not establish independent timekeeping, comfort or dive-performance results. No hands-on, timekeeping or water testing is available to support those judgments.
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Rank #4
- The Seastrong Diver Extreme Automatic is housed in a 39 x 40.50mm steele case and features three central hand-polished hands that sit at the heart of a dial textured with Alpina's iconic triangular emblem, punctuated by a date window at 6 o'clock.
- For maximum readability, both the hours and minutes hands and the hour markers have been coated with luminous material and the date window features black figures on a white background.
- WR to 300m, and comes on a bright orange rubber strap.
Rank #3
- Water-resistant to 300M, this 42mm Seastrong Diver 300 Heritage Automatic with steel case lets you measure your immersion time in hours, minutes and seconds. Its black lacquered sunray-brushed dial features gold plated luminescent hands, making it easy to read, even in the low light of the deep sea. Featuring a modern automatic caliber with 38 hours power reserve and an anti-scratch sapphire glass. Comes with two straps, one in brown calfskin leather and the other in beige topstitched rubber.
- Hours, Minutes, Seconds
- Silver-Tone Stainless Steel
- Anti-Reflective Sapphire Crystal
- 30 Meters and 3 Year Limited Warranty
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.
