Yes, I think Omega might have had dials in stock for some time and some models, but I don´t know how long stock might have lasted for common models/references. There need not be a chronology of dial manufacturers used, dials have been sourced from various distributors at the same time, depending on models to be put on. In the archive of the Omega Museum they keep a binder with vintage B&W photos of various dial samples which were provided from various dial manufacturers at the same time.