Firstly a new Mulberry Roxanne is £595 so if it is listed on Ebay for much less than this guide price chances are it is not authentic. You will see pre-owned bags but again you will not pick one up for £100-£200 so ask if the seller has any proof of purchase. One way of spotting a terrible fake (which i have seen on sale here at Ebay) is to look at the side flaps that have the D ring hanging from them , they should be suede at the top and leather at the bottom the obvious fakes are all leather. Another thing is the round copper disk inside the bag if it has a serial number on it be wary i have not seen a Roxanne in a department store with a serial number on it. If there are limited pictures on the listing ask for more to be shown this will also be a good sign that the bag is in the sellers possession and is not being sent from a bag supplier in China or the likes. Inspect the pictures closely and match to those found on the Mulberry website to compare the quality of the bag. Check the sellers items for sale link if they have more than one Mulberry listed it is unlikely they are the "real thing". Do not be scared of asking questions establish where and when the item was originally brought and how much it cost.Check the colour of the bag if in doubt contact Mulberry direct to see if they have produced a bag in the colour listed.