Omega Speedmaster Movements: 1861 vs. 1863 - Bob's Watches
Omega Speedmaster Chronograph Stahl Handaufzug Herrenuhr Ref.... for AED16,428 for sale from a Trusted Seller on Chrono24
Watch Service: Omega Speedmaster Professional. Cal 1861. (The Moon Watch) – The Watch Professional
File:Detailed view on chronograph pushers and crown (with open watch movement) of an Omega Cal. 1861 chronograph movement from an Omega Speedmaster (cropped).jpg - Wikimedia Commons