Back before texts, e-mails, and telephones, the visiting card played an important role in social intercourse in upper levels of society. If a high-ranking person left a visiting card at the home of a lower-ranking person in the social order, that was an indication that social doors were beginning to open; it didn’t require an actual visit from the higher-ranking person.
One use of a visiting card was when a person temporarily in a city was leaving, and would make a round of calls to individuals who had welcomed the visitor into their social circle. Again, it wasn’t actually necessary to have a visit, simply leave the card, marked “P.P.C” for “Pour prendre congé” (French for “to take one’s leave”), to indicate one’s appreciation for the other’s welcome.
There was also a code for turning the corner of visiting cards, where different turned corners, singly or in combination, each carried a particular meaning.