Collectors hold different positions here. Some advise buying exclusively from professional dealers ('Buy the seller'), since private sellers often lack sufficient expertise. Others argue that even professional sellers do not necessarily have more know-how and that private sellers with a good rating history can quite well enable reputable bargains. An unfilled service guide is not regarded as evidence against authenticity, since many originals are sold without entry. Anyone wanting security in nib exchange and warranty performance fares better with the specialist trade.