Sorry if this information has been covered before, but I searched TGP and didn't find it (I did see this related and interesting thread: http://www.thegearpage.net/board/showthread.php?t=344409). I have a 1972 Fender Twin. I dated it based on this article from Greg Gagliano: http://www.tcguitar.com/articles/gagliano_pt5.html. I should say that it is not stock. It was modded long ago to have a single (now vintage) JBL 15. Anyway, it does not have the master volume push-pull knob. It is my understanding that some (I'm guessing late) 1972's had that circuitry, but that it is considered to have been introduced in 1973. It sounds like most players consider the amp to be better with the older circuitry. A store manager that had another 72 for sale told me that those without the push-pull knob had the "blackface" circuitry, but in reading about it, that looks like it is not correct, although the pre-73 circuitry sounds closer to blackface specs, and easier to get closer to that. My questions are: 1. Are my facts reasonably straight? 2. Is a '72 Twin without the push-pull worth more than one with it (not that I have any intention of selling this amp)? 3. Do you agree with the suggestion that I keep the single 15 since it is a "classic hot rod" set-up, like a '57 Chevy with a later 350 small block? I know that the answer depends on my use of the amp. The story of this amp was that I bought it in '98, '99 or 2000 from a yard sale (driving by in the early afternoon, saw the Fender script in the open garage). The woman who sold it to me was the niece of the guy who had owned it -- she implied that he had died. She told me that he was a country player.