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Top-tier supplier movement
Medium-large: suits wrists 6.5 in+ (16.5 cm+)
42 mm case. Wears confidently on average to larger wrists. May overhang on slender builds.
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Authentication
The Seastrong bezel must rotate counterclockwise only; both-direction rotation means the ratchet has failed and the 300m rating cannot be trusted.
Known issues in the market
- Bezel ratchet wear allowing bidirectional rotation is a safety concern on a dive watch; this is a service-required condition, not a cosmetic issue.
| Area | What to check | What is correct | Red flag |
|---|---|---|---|
| case | Unidirectional rotating bezel | Bezel rotates counterclockwise only; positive ratchet click at each index position | Bezel rotates clockwise as well as counterclockwise; worn or failed ratchet mechanism |
| dial | "Seastrong" name on dial | "Seastrong" name present on dial | Missing "Seastrong" text; wrong reference or non-genuine dial |
| movement | ETA 2892-A2 movement architecture | ETA 2892-A2 movement layout visible through caseback | Non-ETA-2892 movement architecture; non-genuine movement swap |
Common legitimate replacements
- Bezel insert; Alpina OEM insert for 300m rating.
- Crystal; sapphire standard.
Expert resources: Alpina authorized service; Alpina Seastrong product documentation.
Authentication guide
Last reviewed June 2026
The Seastrong Diver 300 is Alpina's dive specification watch using the AL-525 movement in a 300m-rated case. Caseback diver certification text is the primary document to verify.
Sources: Alpina Seastrong Diver 300 product page.





