This is where you need to do your homework. You can contact the U.S. Patent office for current information. You can find patent numbers on old guitars, pickups, pamphlets, Inventors name, by dates, by Classification and by number to name a few. I’ve often found a patent in a guitar book and looked up that number at the patent office and then it would site other patents that may be similar or have been sited.

You can actually go to some larger libraries that have books or micro-film containing many patents. Once you get started, you will find others that may be similar or again sited with names of the inventor and their patent number. It’s fun to research and lot’s of great information.