Probably the most resourceful compass in the world for artillery; target acquisition and command posts. The 55 is a unique compass featuring both an optical precision sighting system and a SILVA 1-2-3 SYSTEM compass in the same unit, giving unbeatable precision and versatility in the field. The compass has a luminous graduation ring and markings for compass reading in the dark. Once activated by daylight/flashlight it will give light up to 4 hours of light. 360 degrees on the graduation ring and 6400 mils + 360 degrees on the sighting scale.