Ah, yes. This is the Speedmaster Co-Axial Chronometer, Reference Number 311.30.44.50.01.002. I call it the transitional Speedy. It blends all the design qualities of the traditional Professional (42mm) into the modern coaxial (44mm) case. It's also got a "transitional" movement. The 3313 is Omega's first coaxial escapement retrofitted into a Frederic Piguet base movement. A lot of these failed at first, so they updated the movement into B and C versions. Mine is a B version, but will get upgraded by Omega to a C when I get it serviced. In the later 9300, Omega built the entire movement around the co-axial escapement. Meanwhile, this model got discontinued. I personally think it's a home run of a model, especially if they could put a 9300 in it. It's got the date window, larger case, and the traditional Speedmaster styling.