Up to this point, I've only printed images for personal use or for friends. I have recently donated a few to organizations for show/auction. Is there a "proper" or "accepted" way to sign an exhibition print? Pencil signature on the mat? Watermark on the print corner? Name on the back of the mat? In other forms of printing (e.g. woodcut, lithograph, etc.), the artist is expected to number prints (e.g. 5/100) with the denominator being the total number of prints run. Is this expected of a photographer as well?