Does this card provide the clue to these codes? On the front, the Aare Gorges. On the back, a cachet 'Hotel Brünig & Terminus/Meiringen', boxed code D 550, and a cachet telling us the card is the 'Property of the Dutch Postcard Archive'! So are the boxed codes just curators' markings?

This card, although the stamp is obliterated with a circular datestamp, was never posted, as it bears no address nor any endorsement querying that fact. It was bought as a collectible and later found its way, I guess with the others in my group, into this archive. Let's keep going, out of curiosity.