The STC 4B/603E is a tetrode pulse modulator. This valve also carries the CV designation of CV398. The P535/1E is also a CV398.
The stitched anode with ceramic insulators top and bottom - essential with the EHT used.
The CV398 print. The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
At the top of the anode there is one gold plated control grid wire visible. The copper supports have heat radiating fins above. The screen grid is also wound on copper supports.
Although distorted by the glass, the screen grid winding can be seen to also be gold plated.
This image of the top of the anode clearly shows the two grids passing flat across the white coating of one of the four rectangular cathodes.
The wide glass tube envelope is 64 mm in diameter, and excluding the B4A base pins is 136 mm tall.
Reference: Data-sheet. Type 4B/603E was first introduced in 1962. See also1962 adverts.
