Two hundred and one diamonds, on a dial that already has a large hole in it. That is the problem this watch had to solve, and it is specific to setting a tourbillon rather than any other complication. The Tourbillon Souverain set with diamonds carries 201 brilliant cut stones across a white gold and whitened guilloche silver dial, coming to about 0.52 carat in total, in a platinum case at 40 mm. The movement inside is the calibre 1403 in 18K rose gold: hand wound, a tourbillon with a constant force device and a dead beat seconds, hours and minutes at 3 o'clock, small seconds at 6, power reserve at 12. Twenty turns of the crown give it forty-two hours. It is no longer offered, and the setting was never carried across to the movement that replaced this one.
A set dial is a plate with seats drilled into it, and every one of those seats removes material from it. On a plain dial that is manageable, because the plate is continuous and the setter can work outward from the middle with the stresses distributed evenly. A tourbillon dial is not continuous. It has a large aperture cut through it for the carriage, a subdial opening for the time, another for the seconds and a reserve indication, so the plate is already pierced in four places before a single stone goes near it. Setting into what remains means working around all of those edges without distorting anything, and the areas closest to the aperture are both the most visible and the thinnest. There is a second constraint here that follows directly from the first one. The setting has to stop cleanly at the rim of the carriage opening, because a stone overhanging that edge would be visible against the moving mechanism every time you looked at the watch, and a gap left short of it would read as a mistake. The tolerance for where that last row of stones sits is therefore very small indeed, and it is the part of the job a setter would be judged on. Nothing else on the dial is looked at as closely.
Two hundred and one stones at 0.52 carat averages roughly a four hundredth of a carat each, which puts them at the smallest end of what can be cut and graded, and it tells you what kind of setting this is. These are not stones anybody looks at individually, and they were never meant to be. At that size a diamond stops reading as a gem and starts behaving as texture, so the dial carries a field that scatters and moves rather than a ring of identifiable jewels. Set that against the vertical tourbillon in the current jewelry collection, which carries 93 baguettes at about 22.50 carats on its case, and the two watches turn out to be opposite solutions to the same question. One of them puts a very large number of very small stones onto the dial and leaves the case entirely plain. The other puts a comparatively small number of very large stones onto the case and leaves the dial to the mechanism. Neither of them is a lesser version of the other. They are different arguments about where a tourbillon ought to be decorated at all, and it is worth knowing that both exist before deciding which of them you actually want. Most buyers only ever encounter one.
Setting the dial rather than the case is the older of the two approaches at this manufacture and the more consistent with the rest of the catalog. It was on the Divine that F.P. Journe first set diamonds, back in 2003, and its dial carried 320 stones coming to around 0.36 carat, which is recognizably the same idea worked at a slightly smaller scale. That treatment then spread outward across the rest of the range over the following two decades. Setting a case in baguettes, as the current jewelry tourbillon does, is a much later and considerably bolder move, and it changes what the watch fundamentally is: a set dial amounts to a finish applied to a watch, while a set case is a piece of jewelry with a movement inside it. This watch belongs firmly and quite unambiguously to the first of those two traditions. The case is plain platinum, the specification underneath is the standard 1403 with nothing altered for the setting, and from any distance at all it reads as an ordinary Tourbillon Souverain that simply happens to catch the light in an unusual way. Somebody across a room would not know it was set at all, which is the point of doing it this way.
A set dial cannot be refinished or reset in the way a plain one can, so its condition is effectively permanent and it should be examined on that basis. Work right across the surface at a low angle under strong light, looking for any stone sitting proud, sitting low, or missing altogether from its seat, and concentrate on the rows nearest the carriage aperture and the subdial openings, where the plate is at its thinnest and the setting is under the most stress. Verify the stone count against the original specification rather than trusting a seller's description of it. Check the platinum case at the bezel and along the lug flanks for the rounding that follows repeated polishing. Then wind it fully, twenty turns from empty, and watch the seconds hand step once a second while the carriage completes its rotation beneath. Have the movement inspected by a specialist rather than a general watchmaker, and establish the full service history, since a constant force tourbillon is not work for an ordinary workshop and a set dial makes any intervention riskier.
