Omega Speedmaster Moonwatch Professional 3861 Hesalite 310.30.42.50.01.001 2021 [Preowned]Overview For over five decades, the Speedmaster Professional was defined by its refusal to change. From the 861 to the 1861, the architecture remained functionally conservative. The introduction of the Calibre 3861 in 2021 ended that lineage. By integrating the Co Axial escapement and a silicon balance spring, Omega didn't just update the movement; they solved the "friction problem" that had dictated Speedmaster service intervals since 1968. The 3861