Wait a minute -- that's no Matisse, that's a fake!

Fakes are fascinating. At least they are in art. And especially if they are by such famous manufacturers of fakes as Han van Meegeren, who specialized in Vermeers, or Elmir de Houry, who concentrated on 20th-century moderns.

For one thing, we are fascinated by such a person's uncanny ability so successfully to work in another artist's style that his fakes are mistaken for, and eagerly bought up as, originals by unsuspecting collectors, dealers, and curators.

For another, we are intrigued -- even if also a bit appalled -- by an artist who would throw away talent and creatively for quick money and the questionable pleasure of deceiving others.

And then, of course, we also can't help but wonder if we ourselves would be fooled were we to come upon such a fake in a gallery or auction house.

To answer that partially, there is no opportunity to see just how we would do in such a situation by Associated American Artists' fascinating and appropriately entitled current print exhibition. "The Discerning Eye."

In it we are shown, together with originals, a number of fakes, forgeries, facsimiles, and direct copies of prints by Matisse, Durer, Chagall, Cezanne, Whistler, Rembrandt, Callot, and others. We are also shown what the beginning collector should look out for in the way of suspicious or forged signatures, differences between early and late states of a print, differences in quality of impression, photographic reproductions -- and any number of other apparently minor, but actually significant, indications that what we think we see in front of us may actually not be that at all.

Detecting fakes is almost always difficult, but most especially so when dealing with 20th-century art. "Modern" art's looseness of execution, its general spontaneity and extreme simplifications, make it an easy mark for forgers.

The fake Matisse included in this exhibition is a good case in point. "Head of a Woman" is a crayon drawing made to resemble a large lithograph. It was probably executed by Elmir de Houry, and bears an uncanny resemblance to other Matisse drawings and prints. And yet, because of its sketchy style, it probably took the forger no more than three of four minutes to make.

In all likelihood, this drawing is only one of several made during a rainy afternoon, and for all we know, a collector in London or Basel may at this very moment be proudly showing off his newly acquired "Matisse" -- not realizing that what he really has is a sister to the fake in this show.

While the Matisse would certainly have forced me (its signature is especially convincing), I would not have been taken in by the fake chagall or Morandi. As to the others. I'm not certain, I would, however, have been momentarily confused by a work notm intended to be sold as an original, but as a photographic reproduction of a Cezanne.

Cezanne's major lithograph "Les Baigneurs" was recently photographically reproduced in exact size for the Nelson Rockefeller Collection to be sold as precisely what it is: a reproduction. Its resemblance to the original is uncanny -- and could easily fool anyone too lazy to take apart its frame to check it more thoroughly, or so eager to buy an original Cezanne print for only possibility that it might only be a reproduction.

The show also includes copies of masterworks made by lesser artists and often at a later date. But while fakes, forgeries, copies, and reproductions make up the most dramatic portion of the exhibition, it also concerns itself with other problems of connoisseurship. Chief among these is the way a print will change from state to state as the artist struggles to perfect to expand his image.

A print can exist in one state -- or in dozens. IT all depends on how many times the artist reworks his plate or stone after pulling at least one impression from it to see how the work is going. For instance, impressions pulled after a print's original working constitute the first state: those pulled after its fifth working, its fifth state.

Now it's easy to see that each state will differ at least to some degree from all those that precede or follow it. As a result, different states of the same print can vary widely in quality and market value -- something any collector of Rembrandt prints knows only too well. (In some instances, the price range between the states of a Rembrandt etching runs into tens of thousands of dollars.)

While nothing so dramatic as that, is included here, we are presented with some excellent examples of different states of particular prints. Among these are works by Besnard, Brockhurst, Corot, dine, and Feininger.

In all, this is an extremely valuable and challenging exhibition -- one that should bring out the detective in its visitors. If nothing else, it should make us wary of "bargains" in the art world, and convince us to research thoroughly any important work of art we are thinking of buying. Or, failing that, to put our trust, at least to a degree, into the hands of a reputable dealer.

At Associated American Artists through Oct. 3.