The Dualmatic (and it's sister watch, the Master Hometime), were part of the "Auto-tractor" project that consummated in 2006, in which JLC was trying to develop it's most robust, but easiest to service, automatic base movement. A number of watches came from this including the Compressor Diving GMT, the Lady Compressor GMT, the Hometime (both dials), the later Compressor Dualtime, and even the Reverso Grande Duodate (but the shaped version, without rotor).
It is an EXTREMEMELY robust movement, and the Compressor crowns are, to me, the best water-proofing system I've seen.
Enjoy!
-Dean