I just realized that the 'ohms' slot, the blue slot,
is filled with a half-card in the illustration.
Cards from the bottom are black, brown, red,
orange (the DC board), yellow and green, the AC
boards..
blue, the current and ohms board, with the ohms
trimmer pots in the middle of a full-length card...
and violet, the power amp.
So, the illustration is an AC and DC machine, with NO ohms. (?)