The 18T56007F01 ALPINE 20K dual gang potentiometer with a pull-out shaft is mostly used on the Alpine 5312 and 5313 models. It adjusts bass and treble.
The shaft is spring loaded, push-pull latch.
20kA audio taper, made by Alps in early 80's.
I also have 20kB and 50kA models, not sure on which units they fit.