Chronometer, with a blue seconds had that moves once a second. Omega made 1000 of them, but there were "issues" and they wrre recalled. Only 17 are still in circulation.
The 30''' (ligne) handwound movement
Unarguably the best hand-wound Omega movement; even ater deacdes the base plates show no wear, something that can mot be said about others. Available in sub and center seconds, regular and chronometer grades
