Most "ancient Roman artifacts" sold by any auction house are going to be fake. Sotheby's, with its reputation for transparency, authenticity, and wealthy clientele, is known to sell fake ancient Roman artifacts, exquisitely forged to look like the real deal - the scammers going so far as to use melted down ancient roman copper coins to cast more valuable artifacts. It was determined that at least 20% of all the ancient roman artifacts sold by Sotheby's to be forgeries, and for ebay the percentage is an astronomical 90%+, this is also true for amber, fossils, Indian arrow heads, and many historical artifacts from other time periods - even historical glass bottles are forged. That's why the best way to grow your collection is to simply do the archeology yourself, otherwise you don't really know what you have.