Removing record trays rockola 1426

Hi guys,

Anybody know the first couple of steps in removing
The record trays on a rockola 1426?

The round chrome knob on top looks like it would
Unscrew but doesn't budge. Don't want to risk damaging this.
I'm not even sure if it's meant to unscrew.

Manual is no help with this.

Thanks for any help

George