The Longines Master Moonphase is a family of automatic watches, not one fixed model. In Longines’ US catalog, the examples covered here range from 34mm to 42mm, with different dials and configurations. Their listed movement rate, power reserve and water resistance are consistent, but price and appearance depend on the reference. This review compares five steel references using Longines’ published specifications; it is not a hands-on test of accuracy, comfort or durability.
What the Longines Master Moonphase is—and which references this review covers
Longines uses “Master Moonphase” for multiple configurations in the Master Collection. The brand’s US listings include 34mm, 40mm and 42mm steel models, with variations in dial and bracelet or strap. The reference number is therefore essential when comparing specifications or prices.
This comparison covers five references listed by Longines: 34mm L2.409.4.97.6; 40mm L2.909.4.78.6, L2.909.4.92.6 and L2.909.4.57.6; and 42mm L2.919.4.97.6. Specifications and displayed prices below are Longines catalog claims, not independently measured results.
How the listed references compare
| Reference | Case diameter | Dial and configuration | Listed US price |
|---|---|---|---|
| L2.409.4.97.6 | 34mm | Steel case, sunray blue dial, steel bracelet | $3,450 |
| L2.909.4.78.6 | 40mm | Steel case, silver barleycorn dial, steel bracelet | $3,000 |
| L2.909.4.92.6 | 40mm | Steel case, sunray blue dial, steel bracelet | $3,000 |
| L2.909.4.57.6 | 40mm | Steel case, black lacquered polished dial, steel bracelet | $3,450 |
| L2.919.4.97.6 | 42mm | Steel case, sunray blue dial, steel bracelet | $3,500 |
Prices are US catalog displays recorded in 2026, not guaranteed transaction prices or evidence of current stock. Longines’ pages show additional configurations beyond these five, including strap, mother-of-pearl, two-tone and precious-metal options; check the exact regional listing for the reference you are considering. Longines 40mm listings, Longines 42mm listing, Longines 34mm listing.
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Movement, power reserve and water resistance
For each of the five references above, Longines lists a self-winding mechanical movement running at 25,200 vibrations per hour and a power reserve of up to 72 hours. These are manufacturer specifications; the listings do not establish independent timekeeping performance or how closely a particular watch will meet those figures in use.
Longines also lists 3-bar water resistance on these models. That is the published rating—not a basis for treating the watch as a dive watch or assuming suitability for a particular water activity. Readers expecting frequent water exposure should factor the stated rating into their choice rather than infer a use case Longines does not specify. The listed models have scratch-resistant sapphire crystal; the 34mm reference’s crystal is additionally described as having anti-reflective coating on both sides.
Rank #2
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Choosing between 34mm, 40mm and 42mm
34mm: L2.409.4.97.6
The 34mm reference is the smallest of the compared models and pairs a sunray blue dial with a steel bracelet. Its catalog price was $3,450. The Longines page also shows other versions in this size, including mother-of-pearl and two-tone variants, so confirm the reference and materials rather than assuming every 34mm model matches this one.
40mm: L2.909 references
The three 40mm references offer the clearest dial-based choice within this comparison: silver barleycorn, blue sunray or black lacquered polished. The listed blue and silver versions were $3,000, while the black-dial L2.909.4.57.6 was $3,450 in the catalog display observed in 2026. Those prices attach to the specific references, not to all 40mm versions.
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42mm: L2.919.4.97.6
The 42mm reference combines a sunray blue dial and steel bracelet and was listed at $3,500. Longines also presents other dial and strap variations on its page. The 34mm, 40mm and 42mm diameters are useful starting points, but catalog dimensions alone cannot determine how a watch will look or feel on a particular wrist; try the exact model in person where possible.
How to set the moonphase
Longines’ brief product-page guidance says to set the moon disc to show a full moon, then advance the crown one click for each day since the last full moon and check that the display matches the accompanying illustration. The brand explicitly advises consulting the watch’s instruction manual before adjustment to avoid transition periods and protect the mechanism. Use the manual for your exact reference; the short catalog instruction is not a substitute for its reference-specific procedure.
Rank #4
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Is the Longines Master Moonphase worth considering?
It is worth considering if you want an automatic mechanical watch with a moonphase display and prefer to choose among several case sizes and dial styles. The official listings provide a clear baseline—25,200 vibrations per hour, up to 72 hours of reserve and 3-bar water resistance for the references covered—but do not establish independent accuracy, long-term reliability, service costs, resale value or comfort. Whether the price makes sense depends on the exact reference and how much you value its complication and design; the catalog specifications alone cannot settle that judgment.
Quick Recap
Best Value
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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.
