How do earrings from one of the most spectacular archaeological finds of the 20th c. end up on the auction block at Christie's?

The story in yesterday's papers about the return of artifacts to Iraq has more facets than the Hope Diamond. One is noted in Jane Arraf's Christian Science Monitor story:

The earrings were found after they offered for sale at auction at Christie’s in New York last December. The catalog listed them as having been acquired by the owner before 1969, the year before a UNESCO convention made it more difficult to trade in antiquities.

The earrings were recognized by Iraqi archaeologists as part of the treasures of Nimrud, excavated in 1989 when an Iraqi team discovered a royal tomb overlooked by previous British excavations. They were believed stolen from the Baghdad Museum before the collection was put into safekeeping in bank vaults before the 1991 war with the US over Mr. Hussein’s invasion of Kuwait.

Christie’s, which had put opening bids at $45,000 to $65,000 for the earrings, withdrew them after the Iraq Embassy launched a formal claim.

As Arraf notes, the Nimrud treasures are "considered one of the most spectacular finds of the 20th century, on a scale of the gold found in King Tut’s tomb." One would think such objects would be easily recognized by experts. And yet, somehow, they appear at auction at Christie's with a phony provenance. Either Christie's authenticators are incompetent, or Christie's is simply leaving the task of spotting illegitimate antiquities to the archaeologists. Either way, it is disgraceful.