200s, Sorado, later non-combo Sonaro(not to mention the circa '67 Sonic II), they're all essentially the same amp, two 6550 or KT88 power tubes that provide 60 watts RMS with a 5ar4 rectifier tube, 80 watt(supposedly)with solid state rectification(first appearing in 1971). Bass, treble, and volume knobs, bass and treble boost switches, whatever the model name, this is the classic Sunn Bass amp. The different names come from the rather curious way Sunn marketed the amps; it changed depending on the type of speaker cabinet the heads were paired with. Now, I'm guessing that what you may have is a transitional model after Hartzell bought out the company from the Sundholm brothers. Your amp shows the '70-onward rectangular grill cloth; I assume there's no rectifier tube, with a metal disc cap where the tube socket used to be or else no holes in the chassis(the solid state rectifier circuit would be incorporated with the rest of amp wiring underneath). In 1972, Hartzell stepped up their push into solid state amplification with the unveiling of Colisseum, Concert, Solos, and Studio transistor bass and guitar amps. They did retain tube heads of course, but consolidated all the redundant model names. The various 60 watt guitar heads became the 190L, and the bass amps became the 190B(In the 1972 catalog it is listed as being 80 watts). Instead of actually printing the new model name on the control panel, they used a black rectangular sticker with the lettering in white. This, I believe, was done as they had a surplus of chassis already manufactured, with the various old names already printed on the face plates. I once had one of the 120 watt, four 6550 bass heads with a sticker that read "350B"(with a solid state rectifier). When I scraped off the sticker, the imprint underneath read "2000s", which of course was the original model name for that amp configuration. What I think you have is this: once the decision was made to unify the model names, perhaps they made up a number of chassis before the actual new name was decided upon. As I mentioned, they had a back supply of chassis with the earlier names, and used them up first. The 190L/190B/350L/350B lines didn't last for very long; by the 1974 catalog the only remaining tube amp, guitar or bass, was the newly-introduced Model T. By that point in time, a 60 watt bass amp would not have much appeal; the wattage wars were well underway(if only I could get Barbara Walters to say that!)and even Fender upped the Bassman to 100 watts. Once again, this is all only my theory, and if your amp is tube rectified, that kinda shoots hole in it. However, if anyone else has more knowledge on the subject, let's hear it. Keep in mind that all of that does not diminish the fact that you own a great bass amp, when properly maintained.
