The sophisticated HM Perpetual Moon is, indeed, a superb example of Arnold & Son's technical and artistic excellence. From the inside out, this new timepiece - with richguillochédials and three-dimensional big moon - surprises and delights. The 42 mm case is created in either 18-carat red gold or in stainless steel and houses the exclusive Arnold & Son mechanical hand-wound movement, the calibre A&S1512. The 27 jewel calibre offers one of the most accurate moon phases on the market, with only one day's deviation every 122 years - at which point a single push on the corrector will keep it in sync for another 122 years. The calibre is also equipped with a double barrel to yield 90 hours of power reserve.