F-84 A-1B Gunsight Leveling Instrument 30X19847
Here is an interesting Cold War / Korean War era instrument kit used to level the A-1B Gunsight in the US Air Force Republic F-84 D and E Thunderjet fighter (and later versions F and G, apparently after this kit was labeled) before flight service. The A-1B sight was a gun-bomb-rocket sight used in versions of the F-84 and F-86 jet fighters.
In its original wooden case, the instrument consists of two main components: a sighting tube, and a bracket to affix the sighting tube to the gunsight. The bracket has one spirit level to ensure that the gunsight body is level perpendicular to the line of flight.The sight tube has a level along its body. When looking through the end of the sighting tube lens which has the smallest hole, and the largest hole pointing forward, an image of the spirit level can be seen projected vertically within the sighting tube. By turning the knob affixed at the joint of the sighting tube and the bracket, the air bubble in the spirit level floats up or down, and can therefore be centered on the index mark in the sighting tube. Sufficient ambient light is necessary to illuminate the spirit level in the sighting tube.
The case measures 9 x 4.5 x 7 inches. The sighting tube is ~6 inches long and 1 inch diameter, and the bracket is ~6 inches by ~3 inches.