In 1985, IWC introduced the Da Vinci Perpetual Calendar reference 3570, becoming a game-changing novelty. Its success led to the mechanism being fitted in other IWC watches, such as the Novecento, GST, Pilot’s Chronograph, and even models by JLC. The 39mm white gold case of the Da Vinci Perpetual 3750 features hinged lugs and is available in various metals with a choice of dial colors. The default option was plexiglass, but a sapphire crystal could be requested. Gem-set cases were labeled as reference 8153, while bracelet options were references 9252 or 9253 for diamond-set cases. Its successor, the 375