From the photos the Stainless Steel and Platinum rollerballs of the Classic size (model 163) mentioned can be identified as originals. An important authenticity feature: all Montblanc rollerball refills have a screw thread; if refills without thread are supplied, this is a clear warning sign. With sellers with few ratings caution is warranted, and an escrow service should be clarified beforehand. Detail photos and critical enquiries help to reduce risks.