National Dobro 6V6
I'm unsure about the manufacture date of this amp. It may well be post-war. The 10" speaker code is: G10RS-C1905-2-45. The CTS pot code is: 31A3107. The layout and circuit are virtually identical to the Valco-produced "Supreme" amps of the late forties and early 50s.
The National Dobro Corp label suggests that this amp pre-dates Valco (or else was assembled using leftover National parts). My understanding is that National was dissolved in 1941 and Valco emerged in 1942. The speaker grill differs from those of the Valco Supreme amps (circular rather than squared off). The resistors appear to be of an earlier vintage than those in the Supreme amps I've worked on.
This amp is pictured in an ad displayed on the notecannon website (www.notecannons.com/index.html) as the "No. 50."
