Security features of a vignette

Hello, I hope I have chosen the right subforum here, if not it can be postponed gladly, thanks. Since I will soon go on holiday and have to drive through the beautiful Switzerland, I need a vignette. However, since I only pass through, I offered an unused vignette at an auction house. This auction was ended early by the auction house and the provider contacted me by mail. He offered me the vignette at the price of 10Euro, but only the goods there nn the money. How am I going to be sure that the vignette is not a fake. Are there any features, I have not been able to cover anything unsavory and have no acquaintance who has the current on his vehicle. Would be nice if someone could tell me what characteristics there can be, or if there are any fake vignettes at all. Thank you for reading and helping in advance.