The C1149/1 is a tetrode pulse amplifier designed for use as a radar modulator with a peak pulse output of 330 kW. The vibration resistant design was for marine radar use.
The anode needs to be connected to a good heat sink.
The ceramic base. The pins are numbered clockwise from the locating notch.
The grids are of cage construction and aligned as can be seen in the image. The cathode is a large diameter cylinder.
The wide glass tube envelope is 76 mm in diameter, and excluding the B4A base pins is 137 mm tall.
Reference: Data-sheet. Type C1149/1 was first introduced in 1963. See also1963 adverts.