Started As Frères Baume in 1830 in Geneva, by brothers Louis-Victor and Célestin Baume, the manufacturer later on partnered with Paul Mercier in 1918, becoming the Baume & Mercier we know right now. During a particularly complicated period of time for that brand, Baume & Mercier joined the Richemont group https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/