Hassan Schroeder noted: >>I have a Bassman 50 with a switch labeled "ground". Interestingly, >>it's a 3-position toggle, so opposite polarities plus an alternate >>universe? dunno... (It does have a 3-prong plug, btw) >>Which raises the question: how would I figure out how old it is, >>gear experts? Neat! A quick check shows that eBay has a '71 Bassman 50 with a 2x15 cab that they are asking almost a grand for! I'd make a cheat-cheat of serial number thingies and run up to a good bookstore and look in one of these reference guides: http://www.amazon.com/3rd-Blue-Book-Guitar-Amplifiers/dp/1886768595 (There used to be these things called 'libraries' but I think you can only find them in museums these days.) Next choice is to register one of your throw-away email addys in a gear-head musician forum (or twenty-six) ... somebody somewhere will know what you have, when it was made, and what it is worth. (I think I had a guy from the Netherlands explain to me that my Guild was manufactured prior to June in 1970 because that is when the EC went in to use differently sized pickups! Seriously. Who would know stuff like that? It's good to know wacky people!) Good Luck & Happy Hunting! RonL.