Don't ask me how I know they work.
However, I am amazed that after all these years they still do what it says on the tin.
The receivers are super regens and they make one heck of a racket all the way up to 50MHz, judging by the noise increase on the P3 connected to the K3 when the CB receiver is switched on.
The power output is difficult to measure, but I suspect it is less than 100mW. The output transistor is a small ceramic device in a package not unlike the BFR91. 1965 technology.
Close examination of both transceivers shows they are in excellent condition after all this time. The leather cases are in good condition and even the telescopic aerials are undamaged. Remarkable!
Time to carefully stow them away with the rest of my growing collection of hand held 'walky talkies'.