Series Number Id: UNKNOWN. Sheet number: 57D NE. Edition number: 3. Battle of the Somme, Gommecourt salient: front lines, artillery intelligence, enemy battery positions, trench mortars and rear organisation 5-2-17. "Ordnance Survey, December 1916." "3rd Field Survey Co. RE (1348)". Detail, grid and contours grey. Overprinted with pecked purple British front line and pecked orange-brown German front line. Overprinted in purple: [German battery positions and arcs of fire]; Reference; list of square positions of trench mortars. Purple, green and orange-brown plates registered with needles. Overprinted green: military tracks and observation posts. Overprinted orange-brown: light railways and supply dumps., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC15; envelope_number: 417.