On the Italian antiquities market, the Carabinieri art squad (TPC) reports significant increases in clandestine excavations and counterfeit art. Thefts from collections continue to decline (-24% in 2013), but increased clandestine excavations are being discovered (+ 32%). Art and antiquity fakery are thriving. Here a chain of operators is involved, fakers, middlemen, authenticators. In 2013, the TPC has registered an increase of 35% of people reported for this offense. It's very much a case of caveat emptor is you buy from a dealer without verifying the paperwork very carefully. Beats me why some collectors tend not to.
hat tip Chasing Aphrodite