Look at it up close under magnification and see if it is truly a woven tapestry, or if it is a printed modern tapestry. If it is truly midieval, you should also see signs of wear, deterioration and stress from the weight of it hanging on a wall. It is unlikely that a textile that old would end up in a flea market, but stranger things have happened! Please provide up close photos and a photo of the reverse side. Also photos of any worn or damaged spots.