GENEVA — Open a newspaper, look at a street sign, type an e-mail and chances are a Swiss design icon is staring you in the face, though you'd be hard-pressed to identify it.

But peer closely at the shape of the letters: If they're easy to read and without unnecessary flourishes, then you might well be looking at an example of the Helvetica typeface, which turns 50 this year.

Helvetica lettering adorns images most people can conjure up instantly, from New York subway signs to the logos of Harley-Davidson, American Airlines and BMW. But much of the time it remains invisible in a sea of print, unobtrusively conveying the message the designer intended it to.

Unusually for the little-celebrated craft of typography — the design and arrangement of typed letters — the anniversary is being marked in grand fashion, with an exhibition at New York's Museum of Modern Art and the release of a film by Gary Hustwit paying homage to what the cult documentary maker calls "one of the most popular ways for us to communicate our words."

"Helvetica is one of those typefaces that everybody knows, everybody sees, but they don't really see it at the same time because it's so good at its job. It communicates efficiently and quickly without imposing itself," explains Christian Larson, curator of the MoMA show, which started yesterday and is due to run until the end of the year.

"It communicates a lot of the qualities we attribute to the Swiss. The idea of the rational, functional, neutral and universal," says Larson.

The Helvetica story started in 1957 in the small Swiss town of Muenchenstein, near Basel, when two designers, Edouard Hoffmann and Max Miedinger, were searching for a way to copy the success of "Akzidenz Grotesk," a competitor's design that was winning over customers at the time.

Miedinger, who once wanted to become an artist before training as a typesetter, came up with a design based on Hoffmann's instructions, and by the summer, a clean sans-serif script had been born, which was given the name "Neue Haas Grotesk."

The company's marketing department soon realized the name would have to be changed to something more pronounceable for an international market. So, to reflect its origins, they called it "Helvetica" — Latin for "Swiss."

A wave of enthusiasm for the postwar, modernist Swiss design style helped Helvetica onto the world stage in the early 1960s, but unlike some other new typefaces, it was never just a fad.

Lars Mueller, a Switzerland-based publisher whose gift to MoMA of a 26.5-pound set of original lead lettering is the centerpiece of the exhibition, says Helvetica is a rare example of something durable in the transitory world of design.

"Helvetica is everywhere," he says. "It has become the perfume city. You would miss Helvetica if it wasn't there."

By the 1980s, Helvetica had secured a crucial place in the original 11 typefaces supplied with Apple computers, so that when the desktop publishing revolution started, it became the default choice for amateur graphic designers.

"Today, Helvetica is the most widely distributed typeface in the world, if you discount Arial," says Otmar Hoefer of German company Linotype, which now owns the design.

Of the countless clones produced to imitate the original, Hoefer says only Arial — the design Microsoft Corp. created for its Windows computer operating system — has seen more exposure through its use in e-mails and word processing software.

While Helvetica is still a best- seller, copyright rules mean new variations have to be developed every 25 years. This has allowed Linotype to solve some of the inconsistencies in the original design, says Hoefer.