This valve from Peter Russell Products has no identification. The original Type designation was probably carried on a paper label in the same way as GPR3. The address is for the office and no manufacturer of P R valves has been identified.
The distinctive red base cap.
The very small diameter anode with grid and single thread filament.
The grid is fixed to a single side support.
The valve looks to be soft with the gettering having almost disintegrated. Imaging the inside is difficult but here is a reasonable internal shot.
The balloon envelope is 44 mm in diameter, and excluding the B4 base pins is 95 mm tall.
