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
Omega 72208601208 Cal 1861 Speedmaster Chronograph Mainspring Part NEW (U77) | eBay
SALE] Omega Speedmaster Professional 3570.50 - cal 1861 from 2002 - FULL SET w boxes & papers : r/kabaclyde
Omega Speedmaster Professional Caliber 1861 (4) - SpeedyWatches