I am about 99% sure that this is from the San Benedetto collection. The bag you have is probably from the Thompson Street leather collection. The San Benedetto has beige suede lining and was made in Italy, came in black leather and I believe included a Mia shape. It's from early 2003.
Sometimes it's difficult to tell with a plain leather bag, but I do believe it is San Benedetto. In any event, it is definitely authentic.
~Kat
