You can research your Flow Blue china by looking in a book like "Gaston's Flow Blue China Comprehensive Guide, Identification, and Values" by Mary Frank Gaston. Published in 2005, this, and other older books can help you identify your piece.
You may be hard pressed to find someone else to valuate your items for free online. Deciding the value of older dishware takes some time and few people are willing to put in that time for free. But you can do that yourself by looking at Flow Blue auction sites and dealer sites and checking out sold prices for the kind of item that you have.
Check to see if there is more information on the backstamp. Remember that during the Flow Blue collecting hay day many reproductions were produced. If your piece is indeed authentic, it will be quite valuable. After all, these kinds of sets were often used so easily broken. Handles easily snap off or the two pieces separated.