The calling card was an essential social tool during the Regency. As soon as a lady arrived in town, or prepared to leave it, she dropped off a card at the homes of her acquaintances to let them know. Cards were placed on a silver salver and presented to the mistress of the house who then decided whether she was "at home" to the caller.
A lady's calling card was roughly 2 x 3 inches, smaller than a gentleman's. It was carried in a card case like the one below.
Historical and classical motifs were popular on calling cards in the 18th century (see Mr. Chase's card). But by the 19th century plain cards with just the sender's name and title were popular. However, special attention was given to typeface.
Morning and Evening Calls, Gaskell's Compendium of Forms
Cards and Visits, Etiquette in Society by Emily Post
Paying Social Calls, The Jane Austen Centre
Calling Cards and the Etiquette of Paying Calls, by Michelle Hoppe
Visiting Cards of the 18th Century, Chambers' Book of Days 1869
#27 After Luncheon, Morning Calls and Visits; Chapter 1: Mrs. Beeton's Book of Household Management; items 27-32
The Etiquette of Using Calling Cards, Jane Austen's World; May 21, 2007
The Gentleman's Guide to the Calling Card, The Art of Manliness
The Card Case Forum
Calling Card Cases by Marni Andrews