[Boatanchors] SX-73 Question

[Dave Aabye]

Got a question regarding removal of the front panel on the SX-73 (or R-274).
 
There is a small disk (about 1-inch diameter and 3/16-inch thick) beneath the tuning knob.  It has three srews around the perimeter and one in the center.  
 
I can't tell what's behind this gizmo.  Does anything need to be done with this before removing the panel?
 
Any other tips, preacutions?
 
Thanks and 73 de Dave, W4QCU
Oak Ridge, TN