Seriously, copyrights in America are owned by the person who authored the letter, book, schematic, music, or whatever. American trademarks are goverened by first use. Then there is the issue of "fair use" which says you can reference protected materials in certain conditions. In any case, this place is a cooperative arena that I think you and I and everyone else would agree wishes to be, well, cooperative.

I don't have a problem with your putting "Guinevere" or "ART" on your amp's front panel. I can't speak for the others, but I don't think anyone will mind. I'd be kind of bummed if you didn't.