[R-390] Half moon guard?

[Gord Hayward]

What is the "half moon guard"?  I have wondered what the 4 tapped holes 
around the kc knob are for.
Of course, I'm a newbie in the R-390A realm. :-)

73 de Gord, VE3EOS.

BTW:  My restoration is going well and my R-390A is performing 
beautifully.  There is hum when I turn
on the limiter but I suspect a leaky cap.  I haven't fixed up that area yet.

-- 

Gordon L. Hayward, Ph.D., P.Eng.,
Associate Professor, Biological Engineering,
School of Engineering, University of Guelph,
Guelph, Ontaro, N1G 2W1.