Omega · Manual Wind

1861

The hand-wound chronograph caliber of the Speedmaster Professional. Based on the Lemania 1873, it descends directly from the caliber 861 that replaced the column-wheel 321 at the end of the 1960s; the 1861 is essentially that movement with rhodium plating, adopted in 1996. Its chronograph is cam-actuated rather than column-wheel operated — simpler to produce and to service, which is part of why the architecture survived largely unchanged for decades. Omega used it in the Moonwatch until the METAS-certified 3861 took over in 2021.