How to discern an original oil from a reproduction print.(Chicago Tribune)

Q. When I bought this picture it was backed by a piece of cardboard covered with plastic. I paid $7.50, and I was hoping you could supply me with some information about it. It's signed Marco de Gregorio.

_Joanne Trussell, Long Beach, Miss.

A. Marco de Gregorio was an Italian artist (1829-1876) who painted highly detailed depictions of villages, taverns and children, among other subjects. He worked in oils on canvas and board.

His modestly scaled pictures come to auction occasionally in Rome and Milan but aren't often seen in the American market. The highest price recorded for one of his pictures is $28,578, paid at auction in Milan in 1993. If your piece is an original oil, it would be worth at least $12,000 in a strong European auction.

However, the circumstances surrounding your purchase lead me to wonder whether the work you have is a painting or a reproduction print. Many paintings are reproduced through what's called offset lithography.

There are a few ways to determine if you have a painting or a reproduction print.

First, look at the surface of the work under a magnifying glass. If the image was printed through a photomechanical process, such as offset lithography, you'll see small dots in a tight grid.