Started As Frères Baume in 1830 in Geneva, by brothers Louis-Victor and Célestin Baume, the model later on partnered with Paul Mercier in 1918, becoming the Baume & Mercier we know now. For the duration of a very complicated interval for that model, Baume & Mercier joined the Richemont group https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/