An authenticity check most likely succeeds through careful comparison with documented features as well as assessment based on clear detail photos; in the specific case, the fountain pen was classified from description and pictures as 100 percent genuine. A reputable eBay purchase including personal handover is quite possible, even if the risk of counterfeits remains real. Unproblematic are water-soluble standard inks like the original Montblanc ink; non-water-soluble inks can on longer idle time clog up the feed. Iron-gall inks (blue-black) are also to be seen critically, since they can contain acidic components (formerly even sulphuric or hydrochloric acid).