Radar Indicator Lens, AN/APG-33 and-40 Radar for E-1 Fire Control System
While called a "Flight Indicator" on its label, this is essentially the radar scope lens for the AN/APG-33 and -40 Radar Systems of the E-1 Fire Control System developed by Hughes Aircraft for the US Air Force. These systems were put into use on the Northrup F-89 Scorpion and Lockheed F-94 Starfire Fighter/Interceptors in the 1950's. See images of the scope on the F-94 and the F-89 (instrument panel from the F-89 flight manual). Made by Hughes Aircraft, part number 435-62-0001. This has also been observed on the Canadian Avro CF-100 Canuck (see cockpit image).
The E-1 fire control system used the APG-33 or -40 radar to continuously measure the range, azimuth and elevation of the identified target and allow the observer to take control if the “blip” was identified as unfriendly.
As found AlternateWars.com:
"Produced by the Hughes Aircraft Company, the E-1 was the first in the E series of sophisticated fire-control systems that were to equip more modern planes. The Air Force ordered the system in June 1948, when it asked that the AN/APG-3 radar (being developed for the tail defense of the B-36) be adapted to the Northrop F-89. A November amendment of the June contract extended the requirement to the F-94. The modified AN/APG-3 radar was redesignated AN/ APG-33 and the entire system, including its A-1C gunsight, became the E-1 in late 1949. It was installed in early F-89s as well as F-94As and -Bs. Low-powered, the E-1 was fairly primitive alongside the E-5 of the rocket-firing F-94C. The system was nevertheless a pioneer achievement."
This twin-lens indicator was fitted to the radar scope projector, which would illuminate the image onto the first lens (furthest from view), which also contains a scale with numerals and markings printed upon the glass. A ring rotates a second lens, which appears to be a polarizing lens to adjust the glare or brilliance of the radar image.
The artifact is in very good condition cosmetically, with the glass intact. It has a service label dated July 1958. Measures 3.25 inches diameter and ~4 inches long.