Phil Hirschkorn: There are only 16 known paintings by Italian Renaissance Master Leonardo da Vinci, and this is one of them. Painted around the same time and in the same style as his "Mona Lisa," this portrait of Jesus Christ is called "Salvator Mundi," meaning "Savior of the World."

Alan Wintermute: He's holding up some kind of orb or globe that represents the world, and he's blessing you, giving benediction.

Phil Hirschkorn: Alan Wintermute, Christie's senior specialist for "Old Master" paintings, says the work has typical da Vinci flourishes.

Alan Wintermute: It has that smoky, shadowy lighting effects that create -- in the "Mona Lisa," the famous Mona Lisa smile -- they create an ambiguous very soft shadowy quality. He looks very directly at you, and you have the sense him looking sort of right into you.

Phil Hirschkorn: Independent consultants say this is a true da Vinci. They dated paint pigments and the walnut panel back to the 1500's and took x-rays to study the brush work. Also characteristic of da Vinci, lapis lazuli, a semi-precious stone used for the blue color. In a stroke of clever marketing, Christie's is offering the da Vinci in the same auction as this massive reimagination of his famous "Last Supper," 60 silk-screened panels by Andy Warhol.

Alan Wintermute: We felt that it did sort of indicate this universal genius of Leonardo, which affects really every generation and every century and every country, all the way up through the present.

Phil Hirschkorn: But nothing compares to the real thing. "Salvator Mundi" is the first da Vinci painting ever to be sold at public auction.