Even with private auctions, legally no counterfeits may be sold; the seller cannot here exclude a right of return. Concrete auction numbers can be reported to the eBay hotline; eBay forwards these to Montblanc as the manufacturer, which checks the auction. Helpful for one's own evaluation is the overview of typical counterfeit features at fountainpen.de/fakes.htm. Since counterfeits are getting visually better and better, the counterfeit problem on eBay, in the view of many collectors, remains permanently.