Striped ink windows are found above all on early 146 models up to about 1960; afterwards initially fully transparent windows were fitted; in the 1980s again transparent, then again striped. A smooth ink window is therefore no counterfeit indicator but refers to a model from the corresponding production phase. Safer than the ink window as authenticity features are the nib (counterfeit nibs often carry imprints like 'Iridium Point Germany/Paris') and the bicolour engraving on the clip ring. With eBay auctions, illustration with stock photos can lead to uncertainty; on commercial suppliers there is a statutory 14-day return right that cannot be excluded.