There's a big difference between a little scuffed paint and raised aluminum ridges that are worn flat. It's common for users to slap the backs on and slide them into position rather than to seat the metal feet of the camera body into the back and then hinge the back into place. I would want to inspect any camera body personally before paying $400 or so. It's just one point to examine when buying a used Hasselblad.

Peter Gomena