The 30F5 is a miniature screened pentode that was designed to operate at the standard TV intermediate frequency of 33 MHz. The IF stages in any superhet receiver are where the main signal voltage amplification takes place.
This valve is also specified by Mazda for operation as a triode, this suggests that it would also provide useful gain at higher frequencies, probably 50 MHz for Band I or 175 MHz for Band 2.
The outer screen has been darkened unlike our other 30F5 where the screen is left bright. Through the holes in the screen the strap between the two halves of the anode is visible. Also the outer two grid wires are easy to see.
The control grid has a radiating fin at the top. This is an English made valve and Mazda were members of the BVA.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 57 mm tall.
References: Datasheet & 1040. Type 30F5 was first introduced in 1957.