I got into buying some of those from ebay a few years back.
Out of the 25 or so I got, only two or three turned out nicely. One was a very fine specimen of a Denarius issued under Constantine the Great that has on the backside a picture of Romulus and Remus suckling on a wolf. It was part of the basically millenium collection of the City of Rome (which was already about 800 years old at Christs birth!)