GUEST: I brought my Willem de Kooning sketch that was personalized and given to my father in 1966.

APPRAISER: How did your father know de Kooning?

GUEST: I'm not exactly sure.

My father passed in 1995.

Willem de Kooning was in Hampton Bays, New York on Long Island... APPRAISER: Mm-hmm.

GUEST: ...and my father was on Long Island as well.

My father was an artist and he met many artists, and he must have been very friendly with him because he called him Jimmy.

My father's name was James.

Only friends called him Jimmy.

APPRAISER: Willem de Kooning is one of the most important American artists of the 20th century.

The style that he's most known for and the artistic movement that he's most known for is abstract expressionism.

It really is what it sounds like.

There's abstraction, kind of a move away from realism and how they should look and more into the expression of it, the movement of something, the thoughts of something, the subconscious ideas of it.

In 1963, de Kooning moved to the Hamptons, to Springs, New York, and what was interesting about that is that there were a lot of other artists living very close by, including Pollock and his wife Krasner.

So it was a kind of place where artists would congregate.

At that point especially, he was always drawing in a way that was free flowing.

It's an exemplary work by him because it, it does show his love for form, but in the style of abstraction.

This is graphite on paper.

It is signed and dated lower right, which is in 1966.

And it says "To Jimmy, and good luck to you, Bill de Kooning."

It's later in his career.

He really became famous for his abstract expressionist works in the '50s and '60s.

What do you think it might be worth?

GUEST: I would love for it to be in the thousands, but I'm gonna say $200 to $300.

APPRAISER: Real de Kooning drawings are exceedingly rare.

A lot of the major, uh, foundations for some of these bigger abstract expressionist artists and a lot of artists in general now do not authenticate works.

What you often have is a situation where it's hard to prove something is authentic.

What can overcome that is provenance, and that's what you have.

And that's what's great, that this was given to your father directly by the artist.

I would put a conservative auction estimate of $8,000 to $12,000 on it.

GUEST: Wow.

Thank you, Dad.

(chuckles) It was his birthday yesterday, he would have been 80 years old.