Just discovered...another even older version!
See the scan below from the 1954 Allied/Knight catalog, courtesy Tom Bryant (thanks Tom!) It's another open chassis type, with three tubes, but the types are different, a 12AX7, a 50B5 and a 35W4. No transformer or iron core inductor, so we assume no speaker driving capability.
We don't know when Knight stopped making this model, but it can be assumed that the other open chassis unit came next, followed by the closed chassis version.
Here are the two versions best documented. The first was known as the Wireless Broadcaster, and did just that. The later, and most common version, was the Wireless Broadcaster And Amplifier, and made a speaker output available. There were built on two different chassis, with the older being more of an "experimenters" type (and rather dangerous!) open chassis without a bottom cover. The tube layout was slightly different too, but the same tubes were used in both designs; a single 12AX7 as an audio pre-amp, and two 50C5s, one used as an oscillator, one as a modulator. The older design is on the left, new on the right below.
Buy the complete manuals for both these types On-Line now!