Series Number Id: UNKNOWN. Sheet number: 57D NE. Edition number: 2D. Battle of the Somme, Gommecourt salient: artillery intelligence, German battery positions and arcs of fire 1-11-16. "Trenches corrected to 7-9-16"; in purple overprint below, "1:11:16". "Ordnance Survey 1916." "1st Printing Co., R.E., 3rd Army (1165)." Detail, grid and contours grey; water blue. German trenches red; British front pecked blue. Overprinted in purple: [Germany battery positions and arcs of fire]; Conventional Signs - Gun. How. [with battery reference numbers]. Purple plate registered with needles., WW1 Trench Map Collection: Box PC16, Envelope 433.