Buren is the brand that came up with the microrotors. Universal Geneve Polerouter and the automatic chronographs from Breitling, Hamilton and Heuer based their caliber on Buren. This watch has a 30 jewel movement, caliber 1322. The highly original Gay Freres bracelet (can be studied closely in our PC/Mac “desktop” web version) is another interesting detail. The endlinks are stamped BU2.