A serial number on its own proves nothing. Fakes circulate both with and without a serial number applied, so its mere presence is no evidence of authenticity. More telling is a look under the clip: on pens of recent date, and the Greta Garbo edition is one of them, the word “PIX” stands proud there, worked in relief out of the material rather than engraved or lasered. Bear in mind, though, that pens from the 1980s carry no lettering under the clip at all and that in the 1990s it was sometimes engraved; on the Agatha Christie it reads simply “Germany”.

Antique fairs and flea markets are a typical outlet for counterfeit pens, as they are for counterfeit clothing or software; a current model at a conspicuously low price is almost never an original there. In case of doubt a specialist dealer will give a firm opinion. Owning a fake is not a criminal offence in Germany, but reselling one certainly is: it can be prosecuted and can expose the seller to claims for damages by the rights holder. In other countries — France, for example — even possession is problematic.