I found a source for the wrench for knurled finish nuts used on older radios.
They have two sizes, 1/2 inch and 5/8 inch. They are a little pricey, but if you
want to remove or tighten those round nuts, without going to extremes, or
messing up a panel, these are the tool to use.
Go to www.gcelectronics.com
and search for part numbers 9358 for the 1/2 inch
wrench and 9359 for the 5/8 inch wrench. They have a great line of other hand
tools as well.
I paid $70 for both wrenches, but they are adjustable and will last many years.
They operate like a pin vise, and have good gripping power. I use tape on the jaws
to prevent panel scratches.