January Jones has done it again.

The Mad Men actress, 33, seriously bared her cleavage in a daring, red-hot Versace gown featuring revealing side cut-outs. (Jones posed nude in sultry ads for the brand's accessories line.)

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Says E!'s fashion police: "With a dress like this...the line between classy and crass is a hard one to walk."

At HBO's after party at Circa 55, Jones told UsMagazine.com about baring all in her Versace shoot. "I loved it," she gushed. "And, as a matter of fact, I’m wearing Versace right now!”

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