I'd post in the Grading & Restoration forum. Even at that, it's really hard to tell in-hand and even harder in photos. I've seen people measuring pages, looking at how much the cover does/does not line up with the pages, etc. The CGC book has some suggestions about looking at the edges for unusual indentations and so forth, but they also admit people have gotten more sophisticated over the years so they can avoid detection. I think the most important thing is to figure out what your options are if you drop big bucks and then gets a purple label. This book probably doesn't drop off as others with restoration, but it would still be a big hit b/c of the high price. I got a relatively expensive book recently, sent it almost immediately for grading, but it took so long to be grade it was outside the buyer protection window when it came back with a slight color touch. The seller just told me to go pound sand when I showed the results. Doesn't seem like smart business to alienate a potential repeat customer, but it is what it is.