This is where the Lune starts: 2003, 38 millimeters, and no other size available. F.P. Journe launched the Octa Lune with a platinum case and a dial of 18K yellow gold against whitened guilloche silver, and built it that way until 2005 before the reference widened to 40 mm and the movement changed underneath. The functions were settled from the outset and never moved: off-center hours and minutes, small seconds at 4:30, a large date at 12 o'clock, a power reserve at 7:30 and the moon phase the model is named for. The calibre is the brass 1300, 5.70 mm high. Everything the Lune became over the following twelve years was already present in this watch, and none of it was added later. It has not been made in this form for twenty years.
Yellow gold on the dial is what separates the earliest Lunes visually, and it is a warmer and more old-fashioned choice than anything that followed. F.P. Journe moved to 18K 6N gold for most later dials, which reads pink rather than yellow, and to white gold for the pale executions. Yellow sits outside both: it is the traditional watchmaking gold, the color of a mid-century dial rather than a modern one, and against a platinum case it produces a contrast that is frankly more abrupt than the 6N pairing manages. Whether that is a virtue depends entirely on what you want from the watch. The whitened guilloche silver does the same mediating work it does across the whole Octa family, occupying most of the face with an engine-turned surface that reads cool, and the yellow gold appears as applied elements against it rather than as a field of its own. Blued steel hands finish it. What you end up with is a dial of three distinct temperatures on a 38 mm face, which is a good deal of activity for a small watch and is held together only by the layout. That the layout manages it is the achievement, and it is easier to appreciate here than on the 40 mm versions, where there is simply more room for everything to sit apart.
The brass calibre 1300 is a different movement from the gold-plated calibre that replaced it, and the specification is worth having in front of you. It stands 5.70 mm high across 223 components, carries 30 jewels, and runs at 21,600 alternations per hour through an in-line lever escapement with a fifteen-tooth wheel. The balance is free sprung, regulated by four weights set into the rim rather than by an index, with an inertia of 10.10 and a lift angle of 52 degrees. Automatic winding brings the rotor round 274 times in an average day, filling a single barrel that holds a mainspring roughly a meter long and delivers about 160 hours, of which the manufacture stands behind the first 120. The plates and the bridges are made of plated brass, which is precisely what the collection designation refers to and is the only thing it refers to, and they were replaced with solid 18K rose gold within a year or two of this watch being made. That is why the movement number changed and why the later Lune reads differently on the dial. Nothing here is a lesser version of what came after. It is a different generation with its own dimensions, and the tenth of a millimeter separating the two movement heights is a real difference rather than a measurement error.
The Octa Lune took the prize for best men's watch at the Grand Prix d'Horlogerie de Geneve in 2003, in the year it was introduced, and that award is a useful marker of what the model represented at the time. F.P. Journe had been selling watches under his own name for about four years. The Octa platform was two years old and had one complication on it. Adding a moon phase to a five-day automatic and having the result judged the best men's watch of the year established the platform as something other than a single good idea, and everything the family did afterward, the Divine and the Calendrier and the Chronographe and eventually the UTC, followed from that position. The watch that won it was this one: platinum, 38 mm, yellow gold on the dial, brass movement inside. The versions that are easier to find today came later and are different objects, made after the manufacture had grown, on a movement built to a different specification, in sizes this watch was never offered in. That distinction gets lost routinely, because the model name did not change when everything under it did. Anybody interested in where the Octa's reputation actually came from is looking at the right reference.
Two things settle whether an example is what it claims to be, and both are quick. The case must be 38 mm, because the 40 mm option did not exist yet in this execution, and the dial must be yellow gold rather than 6N, which daylight will separate immediately once you know to look. Confirm the movement through the caseback: plated brass against solid rose gold is unmistakable. After that the checks are the ordinary ones for a twenty-year-old watch. Look for plating wear at the bridge edges and around the screw seats, ask for the service history and find out specifically who carried out the work and when, and examine the dial under raking light for refinishing, which on yellow gold shows as a flattening of the applied elements. A 38 mm platinum case will also feel heavier than its size suggests, which is worth confirming by hand. Then set the date across midnight with both discs landing together, take the moon through a full cycle, and let the reserve descend its arc across several days.
