In 1977, five years after the release of the Chronograph 1, the team at Porsche Design—still small and experimental—set out to create a watch that merged survival functionality with their signature minimalist aesthetic. The idea came from Ferdinand “Butzi” Porsche, an avid outdoorsman, who envisioned a timepiece with a built-in compass. By August of that year, the concept had evolved into a striking design: a matte black dial with bold white hands, luminous hour markers, crosshair lines, and a subtle, color-matched date window at 3 o’clock. The dial's cross-sectioned design echoed hunting optics and the navigational purpose of the watch. The real innovation, however, lay beneath the dial. The watch featured a removable compass, developed in collaboration with Lufft, encased in sapphire crystal and fully functional outside the watch. On the caseback sat a polished emergency signaling mirror, and the aluminum bracelet featured 5mm-wide links that could be used as a ruler—form following function in every detail, there is a release mechanism in the buckle so you can open up and lay the watch flat as a ruler. IWC, approached by Porsche Design in September 1977, overcame the significant challenge of magnetic interference by modifying ETA 2892 movements with non-magnetic alloys. The final product, reference 3510, launched in 1978 in black and rare olive green anodized aluminum. A technical and design triumph, it remains one of the most innovative tool watches ever created. Brand: International Watch Co. Model: Porsche Design Compass Reference: 3510 Year of Manufacture: 1978 Serial Number: 2265999 Material: Aluminum with coating Dimensions: 39mm Crystal Material: Sapphire Crystal Luminescent Material: Tritium Caliber: IWC caliber 375, 22 jewels. Type of Movement: Automatic Band Width: 18mm Bracelet: IWC Aluminium Box/Papers: Yes, original box. Comments: Complete bracelet, mint condition.