Launched As Frères Baume in 1830 in Geneva, by brothers Louis-Victor and Célestin Baume, the manufacturer later partnered with Paul Mercier in 1918, turning out to be the Baume & Mercier we know these days. In the course of a particularly complicated time period for your model, Baume & Mercier https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/