It was excavated at Nanclares in Basque Spain, and is meant to be the earliest depiction of the crucifixion - and by far the earliest Calvary scene, with Jesus and the two robbers all depicted.
A few others were skeptical, but it was found in an archaeological excavation, and context is key as we keep being told ... so it had to be genuine.
My problem was that the scratched looked too 'clean' - which might simply have been a bad conservator, and a trick of the photographer (I haven't seen the piece).
Plus the inscription on the titulus reads "RIP" [requiescat in pace] not Pilate's mocking "INRI" [IESVS NAZARENVS REX IVDÆORVM] - an acronym popularised in 19th century America. Oh, and RIP also suggests that Jesus is dead, which would be fine for a Jew but goes against Christian theology (the whole point of Christianity is that he is Christ, and does not die in the RIP sense).
Turns out that proper experts have now examined both this sherd and other 'finds' from the excavations, and gosh darn it they turned out to be fakes - an attempt to fake history in the service of Basque nationalism. Guess it's more creative than blowing people up.
Finds that made Basques proud are fake, say experts - The Guardian:
For traditional Basques the pictures, symbols and words found scraped onto pieces of third century pottery dug up near the town of Nanclares, in northern Spain, included miraculous evidence that their unique language of Euskara was far older than ever thought. Eighteen months ago the dig's director, Eliseo Gil, claimed that some finds at the Roman town known as Veleia were on par with those at Pompeii or Rome itself. Basque nationalists bristled with pride. This archeological jewel gave them a far greater claim to a distinctive, millennial and Christian culture than they had dreamed possible.
Now a committee of experts has revealed those jewels to be fakes. "They are either a joke or a fraud," said Martín Almagro, a professor in prehistory from Madrid. "How has something like this been taken seriously for so long?" The hunt is on for an archeological fraudster who defaced fragments of third century pottery with fake graffiti.
Now experts who have studied the pieces in depth say the fakes, some of which used modern glue, should have rung warning bells immediately. References were found to non-existent gods, 19th-century names and even to the 17th-century philosopher Descartes.
The article is worth reading in full.
Since I'm in the mood to call 'Bull' ... I think that this was a student prank on a dig, that the big professors got over-excited about, and it escalated to the point where the student was too scared to confess.