If it's old and dirty with a torn headbadge, then my first guess is that it's the real thing. Why make a replica of something that is not well known and probably a bit harder to sell. But for those who know, you have a jewel - or where are you buying it? .

Most fake bikes I've seen are from popular and famous brands like Cinelli, Colnago and Pinarello. Especially bikes with decal instead of headbadge. And keep in mind that it was hard to get decals and rare parts before internet, so if the bike is untouched after 1995 it's even more likely to be the real thing.