Started As Frères Baume in 1830 in Geneva, by brothers Louis-Victor and Célestin Baume, the brand later partnered with Paul Mercier in 1918, turning into the Baume & Mercier we know these days. All through a particularly difficult time period for that model, Baume & Mercier joined the Richemont group https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/