[stevehertz]

Well, I can't answer your (valve) query in a factual manner, but HMV were always at the cutting edge of technology, so given that the radio was made in 1936, ie a year or even up to say 18 months after the valve range was released, then it's quite feasible and of course you have the proof before you. Otherwise it's most unlikely that someone has changed the valves and bases. To my knowledge the 650 used the same valves throughout production, that is to say, international octal.