Light blue is a steel-only dial in the 37 mm Royal Oak line. It appears on the plain steel reference and on this diamond-set steel reference, and Audemars Piguet issued it in no gold configuration in this size and in no gem-set version. Of the five dials used across the 37 mm references it is also the palest, lighter than grey and considerably lighter than Bleu nuit nuage 50, which places it at the opposite end of the range from the anniversary signature colour while sitting in the same programme. Setting a bezel with diamonds above a pale dial produces a different result from setting one above a dark dial: on a dark ground the stones are the brightest thing on the watch by a wide margin, and on this one the dial competes with them, so the setting reads as part of a bright object rather than as an intervention on a dark one.
The case is 37 mm across and 9.1 mm thick in stainless steel, with the octagonal bezel set with diamonds. That matches the plain 37 mm reference of the same generation exactly, because the bezel stones sit in metal that was already present, while the fully gem-set version of the same case reaches 10 mm since setting the dial and bracelet requires channels cut through both. The eight hexagonal screw positions remain and the run of stones is arranged around them. The dial is light blue with the Grande Tapisserie pattern, the larger of the two grids the collection uses. On a pale ground the tapisserie reads as fine relief rather than as shadow, since there is no dark field for the recesses to fall into, and the pattern is picked out by the difference between the brushed tops and the cut edges of each square. That is subtler than a dark dial produces and less forgiving of any inconsistency in the cutting. White gold applied hour-markers and Royal Oak hands sit above it. The bracelet is integrated steel, tapering from the case with alternating brushed and polished surfaces, and closes on an AP folding clasp. Cool pale blue, cool steel and white stones give the watch a single temperature throughout, with nothing warm anywhere on it, and the absence of any warm accent is what allows a pale dial and a set bezel to sit together without the watch reading as two separate ideas.
The function set is hours, minutes, centre seconds and a date. That is one more than the fully gem-set references in this size carry, since those omit the date rather than break a continuous stone dial with an aperture. Here the dial is metal, the window costs nothing structurally, and the reference keeps the complication the collection has carried since 1972. Centre seconds holds the three hands on a single axis. The applied markers matter more on this reference than on the darker dials, because white gold hands over a pale blue field have limited contrast on their own and the markers supply the fixed points the eye needs. The bezel setting sits outside the dial and interferes with none of this.
The Royal Oak is the collection Audemars Piguet is built on, and the 37 mm anniversary references form a three-step ladder in setting. The plain reference is unset at 9.1 mm, this reference sets the bezel and leaves the dial alone at the same height, and the fully gem-set reference sets dial, bezel and bracelet in a single coloured stone and reaches 10 mm. Within the diamond-set tier the steel references run light blue, Bleu nuit nuage 50 and grey, while the rose gold references run silver-toned, Bleu nuit nuage 50 and khaki green, so Bleu nuit nuage 50 is the only dial crossing both metals and light blue is one of two confined to steel. Each anniversary reference has a standard-catalogue counterpart with the same dial and no anniversary designation. The white gold version of the case sits outside that structure, using baguette-cut diamonds as hour-markers and a baguette-set bezel rather than the brilliants used here.
This reference suits a collector who wants a bright watch rather than a dark one with bright stones on it. Most diamond-set sports watches work by contrast, placing the setting against something that makes it conspicuous, and this reference does the opposite by matching the dial to the stones in temperature and letting the whole object read as one pale thing. That is a quieter proposition than the specification suggests. It appeals to someone who wants the set bezel to look integral rather than added, and to someone who prefers the palest end of the collection's dial range. The trade is legibility, since a light dial under white gold hands asks more of the wearer than grey or Bleu nuit nuage 50 would. Keeping the date and the applied markers offsets that in a way the fully gem-set references cannot. The anniversary designation ties production to the occasion.
