Compressor case may appear conservative with its round design, the functions and features of this watch are anything but ordinary. The main design element unique to the Master Compressor line is the secure rotating bezel set as a key inside the crown to ensure it does not accidently move. Jaeger offers the Master Compressor in Automatic, Chronograph, Dualmatic, World Chronograph, Geographic and Memovox, which incorporates a mechanical alarm function.