One meets the most interesting characters in the archival showroom at Manhattan's New York Vintage. There on the left hangs a rare 1940s gown by Surrealist designer Elsa Schiaparelli. Over on the right, an effusive black '50s Norman Norell cocktail dress (recently worn by first lady Michelle Obama at a holiday event). Further down the rack: a gold YSL number from the '70s.

And then—what's this? This garment looks awfully contemporary.

"It's...