GRANTED, THE SCANDAL concerning the Supreme Court's purchase of the bogus portraits of John and Polly Marshall is two years old and a mite moldy, but a scandal is a scandal, and it is never too late to see justice done.

The judicial side to this story is peculiarly distressing. When the portraits were originally offered the court in 1977, they were judged to be "priceless" by appraiser Victor B. Lonson, who nevertheless set a price on the pair of $107,000 (framed). After the hoax was discovered, the Smithsonian disavowed any knowledge of Mr. Lonson (now deceased) - which answers one question, but raises another: of how Mr. Lonson was able to work in out of nowhere to make his appraisal. Moreover, Mr. Lonson was but one of two appraisers in on the act. Does that mean at least one prankster or inside man remains in the Smithsonian's employ?

Then there is the matter of the discovery of the hoax itself. Two days after the paintings had arrived, they were examined by none other than Chief Justice Warren Jurger, John Marshall's successor, while taking what he calls one of his "inspection strolls." Said Mr. Burger upon espying the portrait of Polly: "It struck me at once that the lady is not Mrs. Marshall" - a striking undoubtedly made easier by the fact that the brass plate on the portrait was inscribed "Lee," whereas Mrs. Marshall's maiden name was Ambler. So far so good, of course, and the chief justice deserves chief credit for his sharp eye. But why was he unable to recognize that Mr. Marshall was also a fraud? And there was this business of the portraits' allegedly having belonged to a Chief Justice Thad Wood, although there never was a Chief Justice Thad Wood. And why didn't somebody tell that to the judge?

All of which brings us to the bewildering problem of how all our venerable portraits - and statues, too - are authenticated in the first place. The bogus Marshall portrait looks a bit like the actor Louis Calhern, whereas the "real" Marshall, at least as represented by William James Hubard's work in the National Portrait Gallery, looks more like the actor John Mills, in knickers. But whether or not one of these portraits is the work of a genuine con artist, how are we to know for sure which face, if either, more resembles the original?

If we were Mr. Burger, we would take heed from this tale and go out and have an official photo taken right now, to avoid a similar mess in the distant future. No one would confuse justices Burger and Marshall these days, but history, like art, is subject to mistakes.