A heads-up - I came across one of these many years ago and it caused me much confusion. I seem to remember that it had two frequency changer valves (i thought 'wrong valve!) and that the signal doubles back on itself (final detector diode in the output valve, then back to the 'oscillator' section of the 2nd frequency changer which was used as a 1st AF amplifier then back to the pentode of the last valve.)
(I may be wrong-was a while ago)
Anyway it was very unconventional. Had me stumped.
As has been said, it's live chassis, so the antenna/earth connections need isolated with reliable capacitors.