Swiss Military GMT NERO, Swiss Made Ronda cal. 515.24 2nd timezone, 1 jewel, silver dial, black PVD plated stainless steel case/bracelet (width 20mm, safety butterfly buckle), screw-down winding crown, sapphire crystal. Case: diameter 42mm, thickness 10.5mm, 20atm water resistant. Weight: 176gr. HS Code: 9102.1100.116 . GMT or Greenwich Mean Time used to be the standard on which all timezones were based. Nowadays GMT stands but for one timezone and has lost its original function to UTC or Coordinated Universal Time.diving watch GMT uses a special Swiss Made quartz movement that indicates a second time zone with a distinctive additional hand. Water resistant to 200 meters and with a heavy duty stainless steel case the iconic GMT comes with a stainless steel bracelet or a silicon strap and is available in a black PVD plating, too.