From The Les Paul Forum
Paul Barth, a nephew of the Doperas and an officer in National, started up a guitar factory in Riverside, CA around 1969 (I was off in Austin, TX, going to graduate school, but a couple of friends had gotten jobs at Barth Guitars). Information is extremely scanty, and I don't know that he ever actually produced any guitars under that name. After the plant faiiled, he opened up a small guitar store in La Sierra, CA, a little town between Corona and Riverside, which is where I met him. I took my wife's Yamaha FG-180 in for a set up, and ordered a factory hard case for a Ventura flat top I owned (man,those were the dear dead days!) as he was a dealer for that brand. It occurs to me that there'd be no way to find such a thing today....Anyway, in the tiny "show room" of his shop was the prototype Fender Telecaster Wildwood Thinline (shown on page 125 of the Gruhn & Carter book) which I thought at the time, and continue to think now, was the ugliest thing I'd ever seen with strings on it. Not long after that, I went off to Northern California to make my fortune and never saw him again.

(note: Bartell was actually started in the early 60's)