Eco-Drive, powered by any light source, eliminating the need to replace watch batteries For a rugged look with a comfortable fit, this military-inspired timepiece fits the bill. with a day-date indicator, luminous hands, 37mm screw-back case, and 100M WR. The black dial provides a backdrop for simple Arabic numerals, housed in a stainless steel case along with a woven green strap with patterned stitching and a buckle clasp. Featuring our Eco-Drive technology – powered by light, any light. Never needs a battery. Caliber number E100.