Longines Master Collection Chronograph Moon Phase

A calendar and a stopwatch on one dial.

Start the chronograph for a task, check the calendar before a journey, glance at the moon on the way home. This dial has work to do between meetings, trains and late dinners. The moon sits inside the twelve-hour chronograph counter at six. Above it, day and month share the thirty-minute counter at twelve; a crescent-tipped central hand points to the date around the edge. Small seconds and a 24-hour indicator occupy the counter at nine.^[1][2]

The reference here is L2.673.4.71.6, the 40mm stainless-steel bracelet model. It matches the reference attached to the retailer title “Chronograph Automatic Moon Phase Silver Dial Unisex Watch.” Longines currently calls this dial Opaline Ivory, with applied Roman numerals and blued steel hands. That is different from the collection’s silver “barleycorn” dial with Arabic numerals.^[1][3]

Longines lists the current watch at $4,150 in the US, before tax. Its automatic, column-wheel chronograph movement is the L687.5, with a silicon balance spring and up to 66 hours of reserve. The case is 14.30mm thick, so the 40mm diameter does not tell the whole story of how it wears.^[1]

The 24-hour subdial is an AM/PM indication of the displayed time, not an independently adjustable travel-time hand. The calendar is not annual or perpetual: the date needs correcting after months shorter than 31 days. If the movement runs down, the calendar and moon display will also need setting again.^[2][4]

A modern collection with a long chronograph history.

Longines dates its first chronograph pocket-watch movement, the 20H, to 1878. In 1913 it introduced the compact 13.33Z wrist-chronograph calibre. The 13ZN followed in 1936, with a flyback mechanism whose patent had been filed in 1935. Flyback allows a running chronograph to reset and begin another timing sequence with a single press.^[5]

Those are milestones in Longines’ chronograph development, not the specification of this Master Collection model. The L687.5 uses a conventional start, stop and reset sequence; it should not be operated as a flyback chronograph. Learn that sequence and use it, whether you are timing part of a workday or the minutes before departure. A dressy dial does not retire the stopwatch.^[2]

The Master Collection arrived in 2005, entirely composed of mechanical watches. Its chronograph moon phase brings elapsed-time measurement together with a full calendar and a lunar display. Keep those functions in your daily routine: read the date at your desk, run the chronograph when there is something to time, and let the watch travel with you rather than waiting for a formal invitation. It belongs to that modern collection rather than being presented by Longines as a reissue of one named vintage reference.^[5][4]

There is older Longines moon-phase chronograph history, too. Sotheby’s documented a reference 6574, circa 1985, with a gilt dial, an 18k yellow-gold case, manually wound calibre 502, date and moon phases. Its catalogue describes a thirty-minute counter and moon-phase display. That is an earlier combination of functions, not evidence that the current Master Collection descends directly from that reference.^[6]

Light dials, fine scales and separate counters.

These two historical Longines share visible details with the modern watch: a round metal case, a pale dial, fine timing scales and contrasting hands. Their counter layouts and numerals are different. Neither has a moon-phase display, and neither is identified here as the original of the current Master Collection.^[5]

For a closer functional comparison, the 1980s reference 6574 adds the moon phase, but its gilt dial and gold case differ from the current steel watch. Sotheby’s illustrated catalogue entry identifies its photographed example and records its condition. It is a different object from the two Longines archive images above.^[6]

The archive images are reproduced at their supplied resolution. Select either photograph to see the original PNG; neither has been enlarged to imply more detail.

The current factory specification.

These measurements and movement details come from Longines’ current US product page, including its detailed specification fields. Older listings for the same reference may quote different dimensions or movement reserves; compare the particular watch and its documentation rather than combining specifications from different listings.^[1]

The nearest alternatives.

L2.673.4.71.2 keeps the 40mm Opaline Ivory dial and adds a blue alligator strap in place of the bracelet. Longines lists it at $4,150, with the same advertised 66-hour reserve and 3-bar water resistance.^[7]

L2.773.4.71.6 is the 42mm Opaline Ivory version on a steel bracelet, listed at $4,400. It retains the chronograph and moon phase, silicon balance spring and advertised reserve of up to 66 hours. It is a separate case size, not the 40mm watch under another retail description.^[8]

For a dial Longines explicitly calls silver, L2.673.4.78.6 is the 40mm silver “barleycorn” bracelet model, at $4,100. The corresponding brown-alligator version is L2.673.4.78.3, also $4,100. Both have a textured dial with painted Arabic numerals rather than the applied Roman numerals of the watch shown here. Their individual specifications should be checked separately.^[9][10]

Choose the version you can wear for a full day of work, travel and dinner, not just the one that photographs well. The choice is not just 40mm against 42mm: it is Roman against Arabic numerals, smooth against textured dial, and bracelet against leather. Size the bracelet for a wrist that moves all day. The shared Master Collection name does not make those references interchangeable.

Start with the 21mm lugs.

The current L2.673.4.71.6 is supplied on stainless steel, not leather. Longines specifies a triple safety folding clasp with push-piece opening and a 21mm distance between the lugs. A 22mm strap is not the correct nominal size for that published opening.^[1]

For a replacement strap, width is only the first measurement. Confirm spring-bar diameter, clearance from the case, strap thickness and the intended buckle or clasp. Longines does not identify this bracelet as an interchangeable quick-release system on the current product page; do not assume tool-free removal or a universal end-link fit.^[1]

If leather is the preference from the beginning, the factory blue-alligator L2.673.4.71.2 is the documented alternative. It has its own complete reference and folding clasp. Converting the bracelet watch is a separate fitting job; an official retailer can confirm the appropriate strap, bars and clasp parts.^[7]

Wear it on the walk between appointments, through travel days and into the evening; a few incidental raindrops need not turn the day into a rescue mission. The water-resistance rating is 3 bar, far below a purpose-built dive watch: this is not the watch for swimming, diving or a soaking. Do not operate the chronograph pushers underwater. Follow the supplied manual for water exposure and calendar adjustment, and have the seals checked as recommended by Longines. Regular wear means respecting those limits, not leaving the watch unworn.^[1][2]

Find the 40mm bracelet model.

The official product page is the clearest starting point for the current L2.673.4.71.6 and its factory specification. Check the complete reference, actual dial, included bracelet links and warranty terms before buying. For an older or pre-owned example, ask for photographs of the watch being sold, its service history and its movement documentation.