A hint for new guys entering the collecting field. Try to keep track of selling price ranges for legit items. I say price range, because there is not set price on anything. However, keep this in mind. When you see a legit item that sells for $100 and up, be suspicious when some guy has an endless supply that is on an auction board at a bargain price.
If the sling in the original post were legit, I would have locked in and purchased every one he has at the $40.00 asking price. So would about 100 other collectors.
Usually the price tells it all, but not always. Unfortunately we also have a dishonest dealer who will take a fake item and sell it for the high price of originals. Then, if you do not know what you are looking at, your will be screwed.