Cynthia, I'm pretty certain it is not at all like a copyright. An inventor friend once tried to get a patent and was turned down because every component existed in some other application already, even though the whole concept was new. He was told that he had to have a unique, never before used component in there, to get a patent.
Tim, Yeah, I have one of those lightning rod mahlsticks. You never fall asleep using it, and the shape keeps you on your toes, too.
I think Lexan plastic may be a good solvent-resistant choice and am going to try it out. I'm sure it comes in gray, however what value gray I don't know. Clear would allow you to paint that little grayscale, and put a signature on the back side, then cover the back in an epoxy, or urethane gray value of your choice. The value scale and signature would be visible through the clear on the front. So, I think I'll mess with the clear first.
Thanks Beth! Bill W. informed us that through his research he has found that ABS makes a good painting surface without the need for primer. The thin ABS gets mounted to 3/8 inch thick Birch plywood to make the panel. Once mounted, you go right at painting.
I'm ordering a sheet of ABS along with a bit of Lexan to play with and see how this all works.
Carl