Atwater-Kent model 40 queston?

[HiFiCanada]

This may sound like a really dumb queston, but I can't get the volume control knob off, so that I can get the inerds out of the box.
I tried to pull and even pried it off the shaft but it's not going to happen without breaking something. I have two Atwater-Kent model 40 radios and on both radios, I can't budge it, I don't see any set screws.
Is the volume control knob suppose to slide off the shaft?