Perry, you really need to try one of your Erie skillets. If they are too pristine to use, I can understand why you wouldn't want to. If that's the case, keep your eye out for one that you could bring yourself to use..they are a pure pleasure to cook with.
Mark, as for the makers marks, I think they can add value, depending on the mark. You don't see the flag or the man-in-the-moon marks very often for example, but I would pay (a little) more for one that had them. They most certainly would not make the skillet less valuable.
Everything you'll ever need to know about Erie pans will be found at the link Cheryl posted. ;)