GUEST: Well, it's been in my family for over 80 years. It was purchased somewhere around 1930 by my great-grandparents.

APPRAISER: In Mexico or in the United States?

GUEST: I believe it was purchased in Mexico.

APPRAISER: Okay.

GUEST: And the painting for some time was in bad condition, and it was hanging behind a door.

APPRAISER: Behind a door?

GUEST: Behind a door in the house.

APPRAISER: Dear.

GUEST: If that door was open, then you couldn't see the painting.

APPRAISER: Well, there are two extraordinarily intriguing words in an artists' catalogue of paintings. And those are: whereabouts unknown.

GUEST: All right.

APPRAISER: My understanding of the painting's history is that it was painted in 1904 by Diego Rivera. And at that point, Diego Rivera, who was arguably one of the most important Latin-American 20th-century artists, was only 18 years old. And this was only, I think, three or four paintings by the artist that are known from that early time. It's a wonderful period, early 20th-century painting. But it also gives hints of his mural style, his technique. And even more so, in a way, his subject matter, which were the workers of Mexico.

GUEST: Right.

APPRAISER: A really terrific image. The painting is oil on canvas. It's signed and dated lower right, "Diego Rivera, 1904." And what's interesting about the signature is, it's a very young man's signature. It's one of his school signatures rather than the more formal, mature signature that we'll see later.

GUEST: Oh, really?

APPRAISER: The research that we found in the authentication process of it is that it had been missing. In the records in Mexico City, it was unknown. Where's the painting? Where is "El Abañil"? Which is "The Laborer." It was an important painting for him in 1904, and then disappeared from 1930 to roughly 1995 or '96, when it was exhibited and authenticated.

GUEST: Now, they have done some restoration on it.

APPRAISER: Yes, it has been lined. But it is in very fine restored condition. Well, I think you have something of a painting trifecta here.

GUEST: Oh, good, good.

APPRAISER: The painting itself is by a very important artist, it has a terrific history of being purchased in Mexico in 1930, and it's a very beautiful and important painting. So, trifectas usually pay pretty well. (laughing) I would be putting a retail estimate on the piece of between $800,000 and $1 million.

GUEST: Seriously?

APPRAISER: Seriously.

GUEST: Oh, my gosh. Oh, wow. Unbelievable-- I did not expect that. I'm astounded. I really don't know what to say. (laughing)