IWC has used the Da Vinci family as the test bed for most of their technical innovations starting with the hexagonal Beta-21Quartz-powered Reference 3501 in 1969. The Da Vinci Perpetual Calendar Ref. 3750 from 1985, invented by Kurt Klaus, was the first mechanical perpetual calendar that eschewed the use corrector buttons to adjust the calendar indications. A year later, IWC presented the Da Vinci Perpetual Calendar (Ref. 3755), the first perpetual calendar wristwatch in a case made of a scratch-resistant black zirconium oxide.