Series Number Id: UNKNOWN. Sheet number: part of Sheet 51. East of Vimy Ridge. "[Enemy Battery] positions map" in black overprint with numbered notes. "Trenches corrected to 6-7-17" in red overprint. Detail, grid and contours grey; German trenches and names red; British trenches to depth of 700 yards and names blue; German battery positions and zone call areas black. Used by Major J. C. Thomson, OC 20th Siege Battery., Manuscript on reverse: H[ostile] B[atteries]. GLOSTER WOOD. Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC20; envelope_number: 643.