[skyscraper]

It's actually cone centric tuning. Here's good info: http://www.philcorepairbench.com/conecentric/

I have a 38-7T. The tuning is quite interesting, basically the knob mutes the radio pulled all the way out, tunes normally in the middle, and locks onto a station preset when pressed in. The inner dial is fine tuning when pressed in. You drag them around the circumference. It's much faster than a regular cord and knob.

I think the assembly used some pot metal, so make sure everything behind the dial is in good mechanical condition before you buy.