The sorting key is used to list the cards in a specific order.

By default, the sort key is filled in by the system with the card reference when the form is created.
If the card belongs to a set, the sorting key is constructed automatically based on the information in the card set IF the sorting key is left empty during encoding
If the card simply belongs to a series, the sorting key is automatically calculated based on the information in the card series IF the sorting key is left empty during encoding
The card set has priority over the series.
If the maximum reference of the series is numeric, the sort key generated will include as many digits as this maximum reference.
This value can always be modified manually by the creator of the form.

The postcard in a broad sense is the heart of this site. It includes all sizes of card stock intended to be sent in the open including photo-cards identified or not

The photo card has the "photo-card" printing mode. If the photo map is identified we can specify the locality, otherwise there are generic localities for each country or province of Belgium.

Different postcards will be created if the snapshots are different for the same map of a series or if the reference number is the editor or if the title is completely different. The variety of colors or presentations or title place will only be specified if this presents crucial information for relatively rare cards.

If there is a coherent set of cards from the same publisher or printer, the card will be associated with a series and possibly a set of postcards. A card set is a subset of a series of cards. See the associated documentation.