The K353 klystron is designed to produce microwave power, probably at 9.6 GHz. The waveguide flange is 42 mm square.
The K353 is a low power device and probably used in portable radar installations and probably as a local oscillator.
Although not listed in the 1971 catalogue it follows the style of other klystrons in the series.
The thin metal tube envelope is 18 mm in diameter and, excluding the base pins, is 67 mm tall.
Reference: Observation & 4014.
Updated March 01, 2013.