I'd love to have an actual go on a genuine 30s National Duolian, although I suspect certain innovations like truss rods, would put me at peace with going home to a modern far eastern made reso afterwards....
Good choice. I think DADFAD (member) may have an early duolian.
Yes, I have a '38 Duolian, and a '37 Style O. (Or is it the other way around date-wise? I guess I'm getting senile!)
The Duolian looks like it was probably originally a square-neck, but sometime in it's distant past (quite a long time ago judging by the finish) the neck was rounded (maybe even factory as it was a nice job and the finish is the same on the whole neck).
Those old Nationals, whether round or square necks, had old-fashioned flat non-radiused fret-boards that sometimes takes a little getting used to by guys who are more used to playing more modern radiused fret-boards. (My '30 L-1 and '34 Jumbo Gibsons also have those old-style flat fret-boards.)
As far as not having a truss-rod (while I'm not familiar with new reissue Nationals construction), necks on the old Nationals can be adjusted from inside the guitar. They had a wooden extention coming through the body from the neck that rested on a kind of... moveable wooden platform or fulcrum I guess you could call it. The neck was attached to the metal body with screws under the double 14th (or 12th) fret-dots (depending on whether it was a 12-fret or 13 1/2-fret model). Even with the screws in place there was a reasonable bit of adjustment of neck-angle available. If more was needed you could crack out the two dots with a center-punch, change the screws and replace the dots pretty easily. Also, on the resonator-cone is a wooden "buscuit" (attached to the top of the cone with a screw) and on that is mounted the saddle, either one can be shaved or shimmed to lower or raise the string heights.
When I got my first National maybe twenty-five or thirty years ago (my Style O) the body was painted a horrible garrish orange color. You could tell it was home-painted (probably with a brush!). I copletely dis-assembled the metal body from the neck to try to remove it. I had little success (with a rag and turpentine and elbow-grease, I didn't want to use any abrasives on it) and finally decided to let a body-shop in town soak it for me in their solvent tank. He said it would probably take a day or so.
Two weeks later he called me and said "John, they must've had damned good paint back in those days. It's still on there, but I'm gonna leave it in another few days and see what happens."
He called me a few days later and said it was still on there pretty good but he could sort of move the slightly-softened paint around with his thumb now so give it a little more time. About a week later the paint started coming off.
It had actually been painted twice in its past, once white and the second time orange. (Once in a conversation with Bob Brozman he told me that occasionally some people back then thought the old nickel finish was too flashy and tacky and so would paint their guitar.)
Anyway, the plus-side was having all that heavy paint on there for almost fifty years left the nickel finish in virtually pristine condition. So that Style-O guitar is in extremely fine condition.
My Duolian has seventy-five years worth of wear on the body, the nickel is vitually all worn away, but there's still most of the Hawiian motif visable on it. But the neck and action are still very good. That's the one I used for playing gigs (as I didn't have to be as worried about the body getting marred or something). The Style O I only use at home or for more special occasions.
They both have the original cones in great shape, although for that Duolian I used for gigs I'd bought a new replacement cone (again, not wanting some drunk or bar-brawl to destroy an irreplaceable part), and those old cones do definitely sound superior (i/m/o) to the new ones). I also bough it a new cover-plate, and cut off the saddle-guard (which I'd never do to the original cover-plate) because I wanted to be able to use the side of my hand for muting while playing slide (which can't be done very easily on the original fully-guarded cover-plate) and playing mostly slide is what I use my Nationals for.
I also put a full-size microphone inside it (taped to that wooden brace under the cone) which, when blended with a good external mic, has a pretty good amplified "Old National Sound." (The internal-mic alone sounds more like you're playing it inside a 55-gallon drum! LOL!)
Anyway, I really like my old Nationals. And each one has its own silghtly different individual "quack," unlike the newer reissues where every body and (especially) every cone is now made of exactly the same material in exactly the same way and so pretty much they sound exactly the same.