The Blancpain Fifty Fathoms 70th Anniversary Act 3 is a 555-piece limited-edition reinterpretation of the MIL-SPEC, announced in September 2023. Its defining period-inspired detail is a moisture indicator on the dial; its modern case is 41.30 mm across and made from Blancpain’s 9K Bronze Gold alloy. The specifications below are Blancpain’s, not the results of an independent hands-on review or test.
What the MIL-SPEC inspiration means on Act 3
Blancpain announced Act 3 on 22 September 2023 as a 555-piece limited edition inspired by the MIL-SPEC model adopted by the main armed forces of its era. That historical description applies to the inspiration, not to the modern Act 3. Blancpain calls the contemporary watch a reinterpretation of the earlier timepiece, retaining its trademark moisture indicator.
The moisture indicator is the most legible link to that inspiration: it provides a visual sign of moisture inside the watch. The present-day design pairs this feature with a sapphire display back and a black ceramic bezel insert, rather than simply reproducing the historical watch. Blancpain’s historical editorial describes the inspiration’s case as German silver; Act 3 instead uses the manufacturer’s Bronze Gold alloy.
Blancpain’s 2023 launch announcement presents the watch as a limited-edition reinterpretation, while its historical editorial discusses the earlier design.
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The 41.30 mm case is made from Blancpain’s 9K Bronze Gold, an alloy the brand describes as patented. Blancpain says it contains 37.5% gold and 50% copper, along with silver, palladium and gallium. The manufacturer says the gold content prevents the green verdigris oxidation associated with traditional bronze and that the alloy can be worn in direct contact with skin. Those material and skin-contact statements are Blancpain’s descriptions, not independent material testing.
The case measures 13.30 mm thick. Its warm-toned metal gives the watch a bronze-like appearance, but the alloy’s stated composition and oxidation behavior distinguish it from a conventional bronze case. Blancpain’s Act 3 overview explains the material, while the official model specifications list the case dimensions.
Dial, bezel and strap
Act 3 has a black dial with old-radium-type luminous hour markers. A unidirectional rotating bezel surrounds it, with a black ceramic insert. The moisture indicator adds a functional historical detail to an otherwise contemporary package.
The watch is supplied on an interchangeable fabric NATO strap. Blancpain lists a 20.00 mm width between the horns, the dimension to check when considering a replacement strap.
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Movement, reserve and water resistance
Blancpain specifies an automatic caliber 1154.P2, running at 3 Hz with 28 jewels and a 100-hour power reserve. It has a silicon balance spring. Blancpain also describes the movement as resistant to magnetic fields up to 1,000 gauss; this is a manufacturer specification, not an independently verified performance result.
The official model page specifies water resistance to 30 bar. That is the stated rating; it does not by itself replace the manufacturer’s guidance on inspection, maintenance or use in water. The caseback is sapphire, allowing a view of the movement.
For the complete manufacturer specification set, see Blancpain’s page for reference 5901-5630-NANA.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Edition and availability
The edition is limited to 555 pieces. Blancpain announced it in 2023; the official materials cited here do not establish whether it is currently available at retail. They also do not establish a current market price, sales figures or auction value.
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