A compressor case is a type of watch case design patented by Ervin Piquerez SA (EPSA) in the 1950s, primarily used in diving watches. This innovative design enhances water resistance by utilizing external water pressure to compress the case back against the watch case, thereby increasing the seal's effectiveness as the watch descends deeper underwater. Unlike traditional waterproof cases, which rely on constant pressure from screw-down backs, the compressor case only applies pressure to the seals when necessary, reducing wear and tear. This design was further developed into the Super Compressor case, which included features like dual crowns for setting time and adjusting an internal rotating bezel, making it suitable for professional diving. The compressor case technology was a significant advancement in watchmaking, allowing for greater water resistance without constant stress on the seals, and it remains a celebrated innovation among watch enthusiasts and collectors.