Think a few (i.e. every single one) might have questionable authenticity, to be polite.
https://www.ebay.co.uk/sch/simo_373/m.html?item=292926649032&hash=item4433c9f2c8%3Ag%3A-Q8AAOSw-ghb9OWs%3Ark%3A31%3Apf%3A0&rt=nc&_trksid=p2047675.l2562
I think the obverse photo on ebay is clear enough to indicate the wear, but it's another one of those annoying photos that I can't zoom in on - there seems to be loads of them these days. Is it a function the seller has to physically disable?
Because he didn't know your bid. Your bid would have beaten the previous £12, and show £13 as the current bid. So they sniped at £18.50, but this wasn't enough to beat your earlier bid, so you win at £18.50 + 1.