Course Selector, Kollsman ID-322 of AN/ARN-30 Radio Receiver UH-1, C-47, C-54
This is a Course Selector, made by Kollsman, part number 1559-010130, ID-322 as used in the AN/ARN-30 Radio Receiver System (see photos of system and its description in gallery) during the 1950s-60's. According to Designation-Systems.net, AN/ARN-30 was used in versions of the following aircraft: UH-1, H-19, H-25, H-34, CH-47, CH-53, OV-1, B-57, C-47, C-54, C-117, S-2, T-33.
Measures 3.25in diameter and ~5in deep. It is in nice condition given its age. The dial markings are clear and the glass and case are intact. The knob rotates the pointer along its axis to select the desired course heading marked along the perimeter scale. Not sure about the purpose of the small rectangular window above the center, but it could be confirm the aircraft heading is on the selected course once the markings are aligned, but that is a guess.