Well, if there's a diopter thing, I don't know how to get it off; it looks utterly normal to me. Is a +diopter a semi-permanent installation?
I just checked again and at 12 feet, the OM1n puts the image about 4-5 inches high and 4-5 inches to the right of "the real world". Note that I'm not sure if there's an actual parallax error between the viewfinder and the film. I do know that if the focus is off, it's only off a very tiny bit because I shot a roll in this camera, including some macro shots, and they came out pretty good.