Good afternoon! I just acquired this nice 1971 Super Lead to match my other Super Lead! I was hoping you all could take a look and tell me if what you think has been done to it! There is a knob on the back in an old speaker jack, but it doesn't seem to do anything! Originally I wanted to get a Vintage Modern for the wife, and we ordered one - but UPS dropped it inside the truck, so it didn't arrive that in good shape! Then, low and behold this 1971 came up and it was an instant buy! Please let me know your thoughts and how original you think it may be! It's certainly different than my other 1971!!! This is that volume knob on the back....... Looks like a "Rosemary" signature - and Teresa has worked on both of my 1971s! And TWINS!!!