CHICAGO (CBS) — If you’re from Chicago and you’re older than 30, you once knew the tall and iconic building composed of bundled tubes at 233 S. Wacker Dr. as the Sears Tower – and as the tallest building in the world.

Willis Tower. (Photo by Scott Olson/Getty Images)

The Petronas Twin Towers in Kuala Lumpur, Malaysia took the world’s tallest title from the Sears Tower in 1996. But 13 years later, Chicagoans were even more shocked as the name of the building that was changed.

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Sears, Roebuck & Company had sold the building in 1994, but the name remained in place until 2009, when London-based insurance broker Willis Group Holdings moved in and acquired naming rights.

But now, the famous skyscraper’s name is in question again. Professional services company Aon is buying Willis Towers Watson – as Willis Group Holdings has been known since it merged with Towers Watson & Co. in 2015.

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The new company will simply be called Aon.

Complicating matters, there is another building at 200 E. Randolph Dr. – which if you’re from Chicago and older than 30, you once knew as Chicago’s second tallest building and called the Amoco Building – or if your memory is longer still, the Standard Oil Building, or affectionately “Big Stan.”

Aon Center (CBS)

But that building, of course, has been known as the Aon Center since 1999, and houses the U.S. headquarters for the company.

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So far, no one is saying if the Willis Tower will be renamed.