I have done PP F&F for the past 2.5 years as a buyer and seller of $5-10k items. I have 100% feedback and most of those I dealt with did as well. There were not any with neg marks but there were a couple with no feedback. If I had a NOS item, I would absolutely open and test the item and have actual pictures in my ad. So many people are willing to crucify this seller assuming they are the scum of the earth. I think they are simply not thinking and feel that keeping the box unopened is preserving value. Some have made the comment that they can afford the PP fees. I don't know how people still don't get it after almost 3 years. It is NOT about fees, it is the IRS. If this guy takes $10k via goods & services, then he will get a 1099 next year and this will be counted as income. That is the high-level way this has been presented. Maybe there is a loop hole that a tax professional can do to avoid that but it is not clear to most and so no one wants to take that chance.
Now on to answering your question. If I really wanted this piece, I would talk to them. Get their phone number and have a conversation. When you are talking ask if they would be willing to open/test/picture or even FaceTime you. Finally you could offer half of the money and after you get it and test it out pay the rest. This takes faith on both of you.
Our community is mostly awesome with very honest people. The actual scam ads are pretty easy to spot so without seeing that ad for myself, I can't judge.