The Valentine's Day card of an earlier era is almost the definition of a romantic and nostalgic collectible. Often both pictorially interesting and inexpensive to buy, they can be found stacked in boxes among other greetings and postcards at antique markets and malls, frequently at prices lower than you'd pay for a contemporary card.

These cards, both the sentimental and the comic variety, represent traditions that date back all the way to ancient Rome, when mid-February was considered the time to meet and court prospective mates. This led to a later custom in which young Roman men presented women they were interested in with handwritten greetings on Feb. 14th, in the name of the Roman martyr St. Valentine.

Geoffrey Chaucer is thought to have been the first person to link St. Valentine's Day to love, while the first written valentine is attributed to the imprisoned Charles, Duke of Orlean, composed for his wife while he was held in the Tower of London in 1415. By the 17th century, the practice had become established enough for Shakespeare to make reference to it in "Hamlet." The passing of handwritten love notes, sometimes embellished with lace, grew more and more popular, and by the early 19th century, factories started to mass produce them in the form of cards.

In this country, the custom began to grow with the import from England, starting around 1723, of valentine "writers" — booklets containing a variety of verses that could be copied onto decorative papers. The first American publisher of commercial valentines was artist-printer Esther Howland, whose Worcester, Mass. business making elaborate — and expensive — cards flourished from 1849 to 1880. Among Howland's innovations were accordion-folded "lift-up" valentines and softly hued underlays to enhance the coloration of the lace. Hand fabricated in an assembly line system, her cards can be identified by either a red "H" on the back or the initials N.E.V. Co (New England Valentine Company).

Over time, certain symbols and conventions emerged, such as the depiction of the winged Cupid — in Roman mythology, a son of Venus, goddess of beauty and love — shooting arrows dipped in a love potion. Also popular through the ages, of course, have been doves, hearts and flowers — particularly the red rose, believed to be the favorite flower of the Roman goddess of love.

There are many different types of valentines that collectors choose to specialize in. Among them are flowery Edwardian-period postcards, wartime cards featuring soldiers and sailors (these have been made since the Civil War and continued through both World Wars), examples by such famous illustrators as Kate Greenaway, Grace Drayton (creator of the Campbell Kids) and Walter Crane, elaborate cards manufactured by Raphael Tuck & Sons, stand-up valentines, three-dimensional "balloon" cards and those featuring fairy tale and nursery rhyme characters. An interesting ancillary category consists of the cheap pamphlets of verse put out to inspire the composer of his own sentimental or comic rhyme.

And then there is the broad range of humorous cards: Many collectors eschew syrupy sentiment in favor of the comic, sometimes even insulting variety. These "penny dreadful" or caricature valentines were first seen in the 1840s, made by such firms as Thomas W. Strong and McLoughlin Bros., and are still going stronger than ever today.

By the early 1900s, such familiar names as American Greetings and Hallmark had joined the playing field, and other novelty areas began to be developed, such as comic character valentines. Of these, some of the most valuable are vintage Betty Boop, Dick Tracy and Little Lulu. Similarly, cards depicting movie stars are eagerly sought after.

Valentines have long been the No. 2 greeting card in America, second only to Christmas cards in popularity, with an estimated 1 billion now exchanged each year. So there's a plentiful supply available to sort through and explore.

Linda Rosenkrantz has edited Auction magazine and authored 18 books, most recently "Beyond Ava & Aidan: The Enlightened Guide to Naming your Baby" (St. Martin's Press). Visit her baby names website at http://nameberry.com. She cannot answer letters personally. To find out more about Linda Rosenkrantz and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.