The dial turned a rotary switch with twelve positions, corresponding to VHF channels two through thirteen. In each position, the contacts on the outside face of one of the coils would come in contact with electrodes on the switch housing, thus inserting that particular coil into the middle of a tuning circuit. You'd tune the inductance of each individual coil by means of a ferrite core, threaded on the outside, screwed into the inside-threaded core of the coil; you'd turn it and thus screw it in or out of the coil with a special plastic screwdriver (an ordinary screwdriver made of paramagnetic metal would change the inductance of the coil mid-adjustment by its proximity). Dust and corrosion would accumulate on the contacts; techs at TV Repair Shops could buy a spray can of "Tuner Spray" to wash them shiny clean.
Groucho, Lucy, Mercury, Death Valley Days, John Kennedy shot dead, the Maddox and the Turner Joy. Clunk clunk clink clunk clunk, here's the American Broadcasting Network, clunk clunk, National Broadcasting Corporation, clunk clunk clunk Columbia Broadcasting Corporation, clunk clunk back to the Public Broadcasting Service.