[turretslug]

6BW6 is good- essentially a 6V6 structure dimensioned to fit in a B9a bottle and a well-regarded device. Not afflicted with price-boosting woo to the same extent as the EL84 either. Quite often, the pigeon-holing of valves was about intended/hoped-for market rather than actual capability and the "audio" valves on miniature glass-button bases with their very short internal connections and low-loss glass base could often operate effectively and efficiently into the low-VHF region. (Though this could also mean that they could mis-behave and do things that weren't intended!).

Perhaps the original 24V dynamotor had been replaced with a 12V type without the label being changed accordingly? Quite a lot of airborne equipment had 24V dynamotors, but with a 12V option available for those cases where 12V electrics were present. Oh, yes- "dynamotor" is the term often used for this type of converter, obviously a portmanteau of dynamo and motor, I think it's originally a US term and may even have been a trade name that became generic. It's a nice touch that you have the converter but they're prone to all the problems of elderly brush motors generally- hardened/dried-up grease, crumbly brushes, tarnished commutators and shorted/open windings!