I don't know when they started, but Dobro brand on 12 string resonator guitar is something I've had pass thru my guitar tradin' price boostin' hands from time to time.
I'm not the guy sellin' this'un, but a quick websearch for "12 string resonator" brought this one up on Bing as the third entry:
http://www.vintageandrare.com/product/Dobro-12-String-Resonator-21510 I don't play 'em, well I don't play ANY 12 string guitar of any type these days, but my eyes are always open when out and about, never know what'll be in somebody's garage sale y'know.
Heck, could probably write a book about the finds. The headstock sticking up out of a plastic trash barrel at a garage sale that made me pull a U turn on a double highway, tried to act all cool, looked at other items on the tables, and then, "how much y'askin' fer that old geetar over there?" and thirty five bucks later it was in the trunk and on its way to an owner capable of appreciatin' it.
Those kind of deals are still out there, though getting to be fewer and farther between. Keep yer head on a swivel out there, I say.
(Before someone takes this all wrong, there have indeed been times when someone had something that was worth *real* money, like that nice old lady who was trying to sell her son's tobacco sunburst Les Paul Junior. Still like new, in case, with factory strap, picks, the Mel Bay Gibson book and the original sales receipt - and ebony fingerboard no less. "My son bought this when he came home on leave and then when he got killed in Vietnam, well its been in his bedroom ever since." -- I made some phone calls, took some digital pics, a day later it was on its way to a collector and I handed that lady a check that was not small and it was something that she said was really needed at the time. I told her that I knew that because she was trying to sell her son's guitar.) That one was a piece of frozen history.
--Mac