Even a groom’s wedding band wasn’t a given until the 1940s and 1950s. “There was an idea of ‘togetherness’ that was emerging after World War II,” says Howard. “People were experiencing a postwar prosperity, and the lavish white wedding fit into that ideal. Jewelers promoted weddings as a symbol of the American Dream.” According to Howard’s research, celebrity hunks like Humphrey Bogart—the first movie star to don a wedding band—also played a role in bringing this trend into popular culture.

Today, a different set of factors is changing the way couples marry—and accessorize. A July study from the Pew Research Center reflects these shifting ideals. In 1977, only 48 percent of the public favored a household where couples shared domestic responsibilities. By 2010, that number had jumped to 62 percent. And 78 percent of women under 30 currently favor a dual-income marriage model.

Emboldened by these trends, the jewelry industry is giving the mangagement ring another try. In 2009, British jeweler H. Samuel designed The Tioro Ring. Less expensive than a woman’s engagement ring, but a bit fancier than a man’s wedding band, this titanium ring is about half a centimeter wide, embedded with a tiny diamond or two. The most expensive is $204, a bargain compared to the average $5,431 spent on a women’s engagement ring in the U.S. in 2012.

That same year, Dreamgirls star Jennifer Hudson responded to her boyfriend’s proposal with one of her own, and hers came with a custom-made, five-carat Neil Lane diamond ring for him. Michael Bublé also made waves when he sported his engagement ring, citing his Latin fiancée’s native customs. In Argentina, Bublé told a Candian audience, “the boy also wears the engagement ring. That's what she tells me anyway."

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On Jeweler’s Row in Chicago, velvet fingers sparkle under glass cases, adorned with diamonds of every cut, carat, clarity, and color. Women’s engagement rings are abundant: Some are simple solitaires while others have multicolored stones or gems winding around the band. Men have limited options—gold, platinum, or titanium bands between five and seven millimeters seem standard. In some cases, the band is embedded with small diamonds or etched with simple lines, but mainstream jewelers rarely offer elaborate designs for the groom. The aesthetics are simpler, but the gesture itself is significant.

Franco sported his quarter-inch titanium band throughout his five-month engagement. During the ceremony, he moved it to his right hand to make room for the traditional groom’s band. Most men, jewelers find, move their first ring to their right hand in lieu of the stacking that is traditional for most women. Others may simply allow the mangagement ring to play both roles and have it polished up for the big day.

According to Amanda Gizzi, spokesperson for Jewelers of America, big diamond names, such as Tiffany’s or Kay Jewelers, aren’t creating man-specific engagement rings yet. When couples come in to pick out a mangagement ring, they often end up repurposing men's wedding bands. “It’s hard to get a number of how many [men's engagement rings] rings are sold,” says Gizzi, “because we don’t know what the rings are being purchased for.”