Paintings, like so many other things in life, are worth more if they happen to have the right name on them. That is why we research signatures in the hope that we will have an item created by a famous or collectible artist. However, many pre-owned paintings have no signature whatsoever. The vast majority of these are destined to remain anonymous, and this is especially true of antique paintings. That said if a picture has survived a century or more without being destroyed it is likely to be of some merit. It certainly sounds as though you have an item that deserves a professional opinion. The larger, well-known salerooms such as Sotheby's and Christie's all have specialist valuers who have the right expertise to identify potentially valuable works of art. Obviously, I haven't seen your artwork so I can't judge whether it is likely to be a rare and sought after item, but it doesn't hurt to get advice, and auctioneers are often the best people to ask.