Jaeger-LeCoultre has reissued its Master Ultra Thin Moon in a 36mm case crafted from 18K pink gold (750/1000), reference Q1242521. The model has historically been cased at 39mm; a 36mm steel version arrived a couple of years ago, and this pink gold edition now brings that smaller footprint to the gold line for the first time. The case measures 36mm across and 9.3mm thick, finished entirely in polished pink gold, with sapphire crystal on both the dial side and the display caseback, the latter secured by screws. Water resistance is rated at 50 metres, or 5 bar.
The case shrink is the whole story here, and it’s worth being precise about what moved and what didn’t. The movement inside, Calibre 925, is unchanged between the 39mm and 36mm versions. That means the sub-dial at 6 o’clock, which combines the moonphase display with a date function read by hand, now sits closer to the edge of a smaller dial. One practical consequence: the index marker that would normally occupy 6 o’clock is no longer needed, since the sub-dial itself occupies that space. It’s a detail that only becomes visible once you put the identical movement into a case 3mm smaller in diameter, and it changes the dial’s visual balance more than any redesign would.
Case construction and proportions
At 9.3mm thick, the case keeps the slender profile associated with the Master Ultra Thin name, and the reduction to 36mm diameter is really a proportion exercise rather than a wholesale case redesign. The long, curving lugs, polished bezel and clean case flanks all carry over from the established Master Ultra Thin case design language, but scaled down they read differently on the wrist. A 39mm gold dress watch can start to feel oversized for a design built around restraint; 36mm brings the case dimensions back in line with the kind of compact, old-school footprint that dress watches wore for most of the twentieth century. Whether that reads as more correct is a matter of taste, but the geometry argument is sound: smaller diameter, same thinness, and the case now sits closer to the wrist’s natural contour rather than projecting off it.
The gender-neutral read comes from this same proportion shift. There’s nothing in the dial treatment, hand design or material that signals a specifically male or female watch; what changes the wearing experience is purely diameter and thickness. A 9.3mm-thick case in pink gold slips under a cuff easily and sits flat rather than perched, and at 36mm it suits a far wider range of wrist sizes than the 39mm version ever did.
Dial layout and finishing
The dial is silver-coloured with a sunray-brushed finish, paired with gold-coloured hardware throughout: applied, faceted trapezoidal hour markers, a pearl-like minute track, and Dauphine hands that are both brushed and polished. One facet of each hand is satin-brushed and the other polished, a detail that creates a shifting play of light depending on viewing angle, which is a meaningful finishing choice rather than decorative flourish given how much the dial relies on reflected light for legibility. The moonphase disc itself is set against a deep blue, starry background, with the date printed in black around the aperture. The layout is anchored entirely by that 6 o’clock display, and with no competing index at the bottom of the dial, the whole face reads with a cleaner symmetry than the 39mm execution allows.
Movement architecture
Calibre 925 is an in-house, self-winding movement built and assembled at Jaeger-LeCoultre’s manufacture in Le Sentier, in the Vallée de Joux. It runs at 28,800 vibrations per hour (4Hz), is built from 245 components across 30 jewels, and measures 4.9mm thick on its own. Power reserve stands at 70 hours from a single barrel, a figure the brand describes as an evolution over earlier generations of this same caliber. Finishing on the movement includes Côtes de Genève, bevelled bridges and blue screws, visible through the sapphire caseback, along with an open-worked 22K pink gold rotor bearing the JL logo. The movement handles hours, minutes, seconds, date by hand, and the moonphase function.
The watch comes fitted to a black alligator leather strap with a quick-release spring bar system and an interchangeable pin buckle in 18K pink gold, making strap swaps straightforward without tools. It is available now as part of Jaeger-LeCoultre’s permanent collection, giving the Master Ultra Thin Moon line a gold option at the smaller diameter that, until now, only existed in steel.
