i used to have a 73 SG, very very very good guitar !
this seems a bit overpriced though..
nothing wrong with gibson in the 70's..
the only thing is they started moving from Kalamazoo to Nashville in november '73
which for some makes the post 73 guitars "unpure"..
they did have some problems in the transition, but nothing to worry about..
anyways, since this one is a '71, Nashville has nothing to do with it..