The panel is meant to test out different kinds of grisaille, which in dry form is like fine crushed grey earth/dust. You mix it with spirit, vinegar and distilled water and use it to make lines on the front (=contour) and grey and hatched shades on the back (=grissaille). Then its carefully baked at about 160 degrees.
It's the traditional way since medieval times to make stained glassed church windows.
I used a part of a painting of Picasso called "Guernica"; about the first modern air raid in history, by the German Luftwaffe in Spain 1937.
Size about 40x50cm.