The 19th century rules of calling, or visiting, helped to distinguish between people of different social classes.   These elaborate rituals varied over time and place, but those that wanted to move up out of the lower or middle class to a higher social rank had to learn and follow the rules in order to be socially accepted.  The calling card, or visiting card, was an important part of these rituals. The calling card was left at homes or sent to individuals for various social purposes and many complicated rules governed its use.
Almost every etiquette book of the 19th and early 20th century addressed the rules of calling and calling cards.

Etiquette of Visiting Cards by Mrs. L. N. Howard, 1880
“A bit of pasteboard, bearing the name of a person, is, in itself, of course, a very  trivial affair. But all the formalities and social observances of well-bred people have a special significance, among such people, and no means of the interchange of civilities holds a superior place to the visiting card.
It’s language is as deeply significant as that of any other sign-language, and there is a right way to use it as well as a wrong way -a grammatical as well as an ungrammatical way.”

Chapter IV – Visiting in Manners and Social Usages, by Mary Sherwood, 1884

Their Significance and Proper Uses, as Governed by the Usages of New York Society by Abby Buchanan Longstreet, 1889.
Detailed descriptions of exactly how visiting cards should be printed for both men and women.
The visiting card’s “tint, texture and engraving are witnesses to its owner’s habits and to his knowledge of the most approved customs in the social world.”

For more information see:

Visiting & Address Cards
Visiting & Address Cards in Hill’s Manual of Social and Business Forms, 1878