How to ID Eames Sofa Compact  

So I am looking at an Eames Sofa Compact. It has no tags, and is in rough shape. All I know is to ask if it folds, then I can narrow it down to an older HM or a Vitra. What else can look for to ID it as an HM or a Vitra? Are there knock-offs of this piece floating around out there? The upholstry is bad and I want to re-do it in Maharam medium lapis. If I need to refoam it too, does anyone know how much a reupholstry/refoam job should run me? What should I look for? I really want 1960's or 1970's HM.