A Compressor (or Super Compressor) case has proprietary water-proof technology from Ervin Piquerez S.A. (EPSA). Super Compressor dive watches from a variety of companies were popular in the 1950's, 1960's, and 1970's and remain popular with collectors today.
The advent of true dive watches in the 1950's was brought about by many advances in materials and construction, but three areas were especially critical Sealing the crystal to the bezel, sealing the case back, and sealing the crown(s) at the stem holes. EPSA's technology primarily addressed the former two requirements, with conventional gaskets used around the crowns and stems. Although screw-down crowns are common today, they were not typical of the EPSA Compressor cases.
Because EPSA made their cases widely available, Compressor cases became nearly ubiquitous in the 1950's. Over 100 different watchmakers used EPSA Compressor and Super Compressor cases, from Hamilton and Enicar to Longines and Jaeger-LeCoultre. Most used stock EPSA cases, though a few modified the look with crown protectors, different lug shapes, and alternate crowns. Enicar even had a unique bayonet case back and referred to a different patent (Brevet) number than other Compressor cases.
EPSA ceased operations around 1975 and this marked the end of Compressor and Super Compressor case production. In recent years, other case-makers have copied the look of these cases, in particular the dual-crown Super Compressor style, and even the trademark crosshatch-inscribed crowns. Others have produced homages to their Super Compressor watches, notably the Longines Legend Diver and Jaeger-LeCoultre Tripute to Polaris models.
All Compressor cases have a namesake gasket between the case back and the case that is compressed by water pressure for better sealing. The Super Compressor is thus rated for 600 m depth.
Although the dual-crown Super Compressor is best remembered today, EPSA produced a variety of single-crown Compressor cases and even a triple-crown snap-back Compressor for Jaeger-LeCoultre, the Memovox Polaris.
Dual-crown Super Compressors have a crown at 11 minutes to rotate an internal diving bezel, rotating the winding/setting crown to 19 minutes. Most manufacturers still placed the date window, if any, at 3 00. On the Jaeger-LeCoultre Polaris, the crown at 11 is for the alarm, with the bezel crown at 3 00 and the 19 crown for winding/setting. Single-crown Compressor cases place the crown at 3 00.
The first model to appear was the EPSA Compressor. This case used a snap back and was thus not as water-tight as the Super Compressor.
The Compressor 2 has a large, deep case back that still snaps on. This allowed EPSA to produce various case styles, including tonneau and cushion cases.