Arnold & Son Watch Perpetual Moon 41.5 Red Gold 1GLBR.U01A.C200A. A white mother of pearl star in a midnight blue sky. The astronomical moon phases showcase Arnold & Sons creativity and aesthetic flair. Perpetual Moon 41.5 is presented in two interpretations, in red gold and platinum. Its dial features a unique motif, Stellar Rays, as befits this astronomical complication.