B62-453. TELESCOPIC ALIDADE. W & L.E. Gurley Model 580. 11-1/2" long, black lacquered, vertical circle, trough compass. The Model 580 was described by Gurley as the "explorer's" alidade; unlike most alidades that are mounted on a central pillar, this one is built close to the base. Serial No. 433033 which indicates it was made in 1943. In its original 5" x 5" x 12-1/2" leather covered wood case, fully intact brass plaque, corners, straps and buckles. Like new. Fine 300-500