Elven Prince, The Golden Shield

I had found these odd plaques at Micheal's and bought one. I have no idea what they are made of, but painting on it was like painting on plaster. If I do another, I will maybe gesso it first and see if that makes painting on it easier. "Elven Prince, The Golden Shield" is approx. 10 1/2 x 6, Acrylic gold metallic Latex paint and Micron marker. Original and prints for sale