National made a staggering variety of instruments. Although the Spanish neck guitars are now the most popular, it is interesting to note that probably as many as 4 out of 5 tricones for example were made to be played on the lap 'Hawaiian style'. I've worked on all models of National and Dobro instruments, from Spanish and Hawaiian guitars to ukuleles, mandolins to tenor and plectrum guitars. If National or Dobro made it I've probably repaired it.
After their move to Chicago in the mid 1930s, they also licenced their resonator technology to other manufacturers, principally Regal, and it is common to see headstock logos from companies such as Alhambra, Gretsch, Old Kraftsman, Ward and Regal to name just a few, all adorning instruments with National or Dobro cones.
So, if you have a National or Dobro instrument, or, indeed any resonator instrument that needs some TLC please contact me, if any one can help, it's me!