The BVA Series 120 have three "windows" on the dial. One reveals the "Heartbeat" balance wheel, the actual heart of a mechanical watch. Then there are two subdials. The first is a continuous sweep second subdial and the second is a linked (not independent) 24 hour subdial.

In order to showcase this amazing precision movement, Bulova has cut away both the dial of the watch and the back of the case to allow you to see through the entire movement. This is often called a skeleton style watch. Viewing through the front and back of the watch you can see the delicate balance wheel, the gears leading to the hands and even the self-winding mechanism.

Because this is a mechanical watch, the second hand sweeps smoothly instead of jumping from second to second, like battery operated quartz movements. And, since the watch is powered by the movement of your wrist, there is no battery to replace. The watch gathers its energy directly from you!

The Bulova BVA Series 120 Watches ares water resistant to 30 meters (or 100 feet) for carefree wear.

Men's Bulova 21 Jewel "Mini Complication" Automatic Watches: 21 Jewel Mechanical Self-Winding (Automatic) Movement BVA-SERIES 120 Fine Precision 21 Jewel Japanese Movement Mini-Complication Style Design Continuous Sweep Second Subdial 24 Hour Subdial Linked to Main Hour Hand Cut-Away Dial To see the Balance Wheel of the Watch Movement Exhibition Back to see the Self-Winding Mechanism Hardened Mineral Glass Crystal on the Watch Front and Back Luminous Hands and Hour Markers Stainless Steel Case Water Resistant to 30 Meters (100 feet) Hidden Deployment Style Buckle on the Stainless Steel Bracelet or Leather Strap Three Year Bulova Warranty Dimensions: Diameter: 42 millimeters (44 millimeters with Setting Crown) Thickness: 13 millimeters