The Alpina Seastrong Diver 300 Heritage AL-520GR4H6 is a 42 mm, time-only automatic dive-style watch with a green dial and rubber strap. Alpina lists it at $1,995 on its US product page. Its headline specifications are a 300 m water-resistance rating and a 38-hour power reserve, both manufacturer claims rather than independently verified test results. Whether it is worth buying depends on whether those dimensions, its no-date layout and its price match what you want; the available information does not establish how it performs on the wrist or underwater.
What exactly is this Alpina?
This review covers the green Diver 300 Heritage, reference AL-520GR4H6. Confirm the reference before comparing specifications: Alpina sells neighboring Heritage variants with different movement and date details. The official US page identifies this model as an AL-520 automatic and does not list a date display. Alpina’s US product page is the source for the specifications and price below.
Alpina Seastrong Diver 300 AL-520GR4H6 specifications
| Specification | Alpina listing |
|---|---|
| Reference and model | AL-520GR4H6, Diver 300 Heritage |
| Movement | AL-520 automatic |
| Power reserve | 38 hours, as stated by Alpina |
| Display | Time only; no date is listed on the US product page |
| Case | Stainless steel; 42 mm diameter and 12.3 mm thick |
| Lug width | 21 mm |
| Water resistance | 300 m / 30 bar / 999 ft, as specified by Alpina |
| Dial and hands | Green brass dial; silver-tone luminous hands |
| Crystal | Sapphire with anti-reflective coating |
| Strap | Green rubber strap with buckle |
| Official US displayed price | $1,995 on Alpina’s US product page; price and stock can change |
How big is the Alpina Seastrong Diver 300?
The listed case diameter is 42 mm, its thickness is 12.3 mm, and the lugs are 21 mm wide. Diameter gives a useful point of comparison, but those measurements alone cannot tell you how the watch will sit on a particular wrist; no lug-to-lug measurement or hands-on wear assessment is established here. If fit is decisive, try this exact reference on before buying.
What do the movement and water-resistance specifications mean?
Automatic AL-520 movement
Alpina lists an AL-520 automatic caliber with a 38-hour power reserve. The company explains that its automatic mechanical movement winds through the wearer’s arm motion and does not require a battery. The reserve is a published specification, not an independently timed result for this individual watch.
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#1 Best Overall
- 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
300 m stated water resistance
Alpina specifies 300 m, 30 bar or 999 ft water resistance and labels the watch for swimming, showering and snorkeling. That is the manufacturer’s rating; the available product information does not establish independent water testing or a dive certification. A rating also cannot confirm the condition of an individual watch’s seals, so it is not a substitute for checking a pre-owned watch or one that has been opened or serviced before water use.
What are the crystal, dial and strap like on paper?
The green dial is listed as brass, with silver-tone luminous hands. Alpina specifies an anti-reflective sapphire crystal and describes it as impact- and shatter-resistant; that characterization is the manufacturer’s, not a result of independent testing here. The green rubber strap has a buckle. Alpina describes the strap as resistant to sand, sea salt and corrosion, but the page does not establish how comfortable it is or how it wears over time.
Rank #2
- 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 AL-520GR4H6 differ from a related Heritage version?
Reference matters: the related AL-525S4H6 product page specifies an AL-525 movement based on the SW200 and a date at 4 o’clock. Those details should not be attributed to AL-520GR4H6, whose US listing names the AL-520 and shows a time-only configuration. Regional pages may present localized descriptions and prices, so compare the exact reference and the market-specific listing rather than treating the variants as interchangeable.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is the Alpina Seastrong Diver 300 automatic worth buying?
At Alpina’s displayed US price of $1,995, the case for this reference rests on its combination of a 42 mm stainless-steel case, automatic movement, stated 300 m water resistance, sapphire crystal and green rubber strap. It is a more natural fit for someone who wants this particular green, time-only configuration than for a buyer seeking a date display or a smaller case. The published specifications do not answer practical questions such as timing accuracy, bezel operation, low-light legibility, actual comfort or performance during diving, so treat those as unknowns rather than assumed strengths.
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- 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.
For Alpina’s US offering, its Seastrong collection page states a 30-day money-back guarantee and a two-year limited warranty. Those terms are specific to the US offering; check the current terms for the seller and region where you plan to buy.
Quick Recap
Best Value
- Hour, Minute, Second, Date
- Anti-Reflective Sapphire Crystal
- Black Rubber Strap
- 300MM Water Resistant
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.
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.
