this one is a 300B SE
i got to hear this amp last saturday & i could say that it is is one good sounding amp. balanseng-balanse...
it has foot tapping dynamics, punchy bass, & knee-weakening luscious mids...
it was originally installed with 6L6 driver tubes (complemented by, if I am not mistaken, 6SL7 tubes) giving it a bluesy sound. for curiosity's sake, andrew replaced them with EL-34 tubes which made the amp more dynamic.
fyi, as per andrew, prototype pa lang po 'to & still being improved!