They’re not diamonds, but Sweethearts candies —those tiny heart-shaped confections with embossed endearments —may well be the sweetest way to get your message across on Valentine’s Day.

A Michigan man, Mike Waltz, went to extraordinary lengths to collect enough “Marry Me” hearts to propose to his girlfriend in 2004. After buying several bags of the candy and finding only two or three “Marry Me” hearts in each, he e-mailed the New England Confectionery Company (Necco) that makes the candies in Revere, Massachusetts. Someone at the company must have had a big heart, because a few days later, a small box of tiny pastel “Marry Me” hearts arrived at his house.

Waltz’s sixth wedding anniversary is coming up this Valentine’s Day, and his wife, Chris, still has that box of Sweethearts, revealing the proposal hearts in its plastic window. “I’m never going to open it,” she says. “It’s a keepsake.” Mike has his own memento in a valet box on his dresser: a Sweethearts that says, “I do.”

More than eight billion (some 13 million pounds) of the little hearts are sold in the six weeks leading up to Valentine’s Day. Sweethearts make up 40 percent of the Valentine candy market, just behind chocolate, according to Aimee Scott, Necco’s marketing director.

One of America’s oldest candy companies, Necco was founded in 1847 in Boston by Englishman Oliver Chase, who got the business off to a good start by inventing devices that cut candy lozenges and pulverized sugar. Necco first sold confections similar to Sweethearts, but in the shape of scallop shells. Messages written on colored paper were tucked inside the fortune cookie-style candy. Fourteen years later, Oliver’s brother Daniel designed a machine that stamped words directly on the candies with red vegetable dye. The treats became popular at weddings and were considerably larger than today’s hearts as they could accommodate wordy relationship advice such as “Married in White, you have chosen right” or “Married in Pink, he’ll take to drink.” By the early 1900s the shape of the candy had changed from shells, baseballs and horseshoes to hearts. As the little hearts grew in popularity, the missives grew shorter: “Miss You,” “Love U.”

“Our main market is in classrooms – kids, teachers and moms,” says Scott. “Our adult customer usually remembers the candies from their youth and it strikes a nostalgic chord.” The “Marry Me” heart is by far the most often requested, she says. The other hearts, however, have no shortage of bon mots. There are at least 60 cute and peppy messages in this year’s production.

Original mottos from the candy’s first appearance in 1902, such as “Be Mine,” “Be True” and “Kiss Me,” remain very popular. Such classic romantic phrases haven’t changed in more than a century, but others have come and gone. “We try to adjust and change, keeping current with the times,” says Scott. In some ways, Sweethearts are tiny time capsules of trendy lingo of days gone by: “Dig me” “Hep Cat” and “Fax Me” have all made appearances in the past 20 years, only to bite the sugary dust. Current missives reflect the language of popular culture and Internet jargon: “You Rock,” “Text Me,” “Me & U.”

Last year, for the first time, Necco solicited suggestions directly from the public on a special web site. It received more than 10,000 submissions and the company’s marketing team selected the most popular. “Tweet Me,” “Text Me” and “Love Bug” were the top three. In the past, the mottos were tied to themes, such as the weather (“Heat Wave,” “Chill Out” and “Cloud 9”) and pets (“U R a Tiger,” “Go Fish” and “Love Bird”). Spanish versions are also available (“Te Amo”and “Mi Novia”). A few years ago, Necco began producing imprints for fans of the popular vampire novel series Twilight: “Bite Me,” “Dazzle” and “Live 4 Ever.”

The company has also tinkered with the Sweethearts’ flavors. Marketing research showed that children prefer bolder tastes and colors. Out went banana, cherry and wintergreen and in came bright blue raspberry, lemon and green apple. This caused a bit of a backlash from sentimental baby boomers who wanted their old candy back. The company was inundated with calls, letters and e-mails complaining about the change. Facebook pages were created to spread the word and fans ranted on blogs about the new confections: “toxic,” “yuck,” taste like “aspirin.”

The response was similar to but not exactly on par with the outrage over New Coke in the mid ’80s – after all, the rock-hard treats were never really about the taste, which was always, a bit chalky to me. The basic Sweethearts recipe consists of corn syrup, sugar, gelatin and food coloring mixed into a Play-Doh-like ball before being rolled flat for printing and cutting.

In an attempt to appease critics, Necco went back to its test kitchen in time for this year’s Valentine’s Day and adjusted its formula. This batch will be a little softer and chewier, says Jeff Green, the company’s vice president of research and development. “We toned down the flavors just a bit; the change was very subtle.” Whether it will be enough for diehard fans remains to be seen.

As for this year’s mottos, with 10,000 suggestions, the company had plenty to choose from and has gone back to using themes. “The majority of them involve movement,” says Scott. So this Valentine’s Day expect to see “Move it,” “Rock On” and “Go, Go, Go.”

Not the most romantic, but naysayers should be relieved that the candy-maker continually nixes the occasional consumer suggestion for “break-up hearts.” Some of the rejects: “Get a Pre-nup” and “Call My Lawyer.”