Late 1930s National, formerly owned by Harvey Dow Gibson
RM-1 resophonic mandolin
with hot plate
Just when you think you know everything, along comes a new piece of information. I used to believe that National Resophonic got into electric mandolins a few years after the other big makers. That was before I started stumbling across instruments like the one on the right, dated as early as 1934, and the one above, which is probably a few years later. That would make National the second company to produce an electric mandolin—three years after Rickenbacker, but two years before Gibson and Vega. How many of these instruments were produced I don't know.
I do know that in the late 1930s, the company introduced its Silvo pickup, which was mounted in a flat, round, black plate that replaced the resonator cover on a National metal-body mandolin or guitar. The resonator cone was also left out of instruments with Silvos. Such instruments appeared in the National catalog for a couple of years; players could also send their Nationals back to the factory to be retrofitted. Apparently, Silvos were not a big hit; National soon abandoned them and started designing other electric guitars. (They later made some more wood-bodied acoustic/electric mandolins under the Supro brand.)
There are still a few Silvos around in playable condition. The late Mark Heard owned one, and recorded a fantastic album with it called Satellite Sky. I once got the chance to play his, and after several years of searching, wheeling, and dealing, I've managed to get one for myself. (Now if only I could play it like Mark ....)
Of late, National has begun offering its new RM-1 resophonic mandolin with a "hot plate" pickup attachment designed by Jason Lollar. These sound fantastic and have been embraced by blues artists like Rich DelGrosso and Bert Deivert.