art by Michel de Gallard

I have a piece of art by Michel de Gallard, but I'm stumped as to what it is. First of all it is on paper like a print, and there is a copyright symbol followed by D.J. in bottom left corner. Here is the confusing part, instead of being smooth like a picture or print, the heavy black areas of the work have texture to them as if they had been painted, but I don't see brushstrokes, rather, there is a roughness to it, comparable to a light sandpaper. The orange signature in bottom right corner is raised(not rough) and that does look to my untrained eye as if it was painted. Also, there is a little warping or bowing to the paper like it had been painted, paper got wet, and shrank a bit as it dried, to give the warped/bowed appearance. Without me even asking, a gallery has offered to sell it on consignment for me, knowing what I've just told you, which leads me to believe I just might have something of value. Do you know what this kind of work is called? It measures approximately 33' high x 22' wide. Any help would be greatly appreciated...Bonnie Rock