A Compressor Case is a type of watch case that increases its water resistance as external pressure increases, using the pressure to compress the case back against the gasket, enhancing the seal.
A compressor case uses external water pressure to push the case back against the gasket, increasing the seal tightness as depth increases. Unlike traditional dive cases that rely on constant screw-down pressure, compressor cases become more water-resistant as you go deeper—the pressure that threatens the watch also protects it.
The Super Compressor case, developed by EPSA in the 1950s, enhanced the original compressor design by adding dual crowns: one for setting time and one for adjusting an internal rotating bezel, all without opening the case. Notable examples include vintage Blancpain Fifty Fathoms and Longines ultra-chron dive watches.
Modern dive watches use screw-down crowns with multiple gaskets rather than compressor mechanisms, as advances in gasket materials and case engineering have surpassed the original compressor concept. However, several brands including Jaeger-LeCoultre have revived the dual-crown Super Compressor aesthetic in modern reissues, though without the original pressure-compression mechanism.