This is a piece of doped German Tarnstoff or 'lozenge' printed aircraft fabric showing 4 of the 4-color uppersurface day pattern.   It measures about 7 inches by 2 inches.  Written on the back is “From. Fok D.VII (OAW.) 4513/18.”  It was part of an order of 200 aircraft with serial numbers 4450/18 to 4649/18 which most likely entered the war in August or September of 1918. The last image measures the number of threads per inch as 50. The ink and handwriting do not look contemporary to the period.