Proof Twenty singles affixed to sheet of laid paper, in shades of red, red-brown or plum, headed "Fugitive Ink printed without oil." (four examples) and "Fugitive ink printed with oil.", each example with ink endorsement alongside indicating whether the ink or paper had been treated with Prussiate, Magnesia or Tartrate or had been left plain. Eleven of the examples show a black ink cross presumably to denote their unsuitability. Photo in colour