Series Number Id: UNKNOWN. Sheet number: part of sheet 36. "Trenches corrected to 9-2-18." "Field Survey Co., R.E. 5781 [number crossed out and replaced with blue overprint] 5810". Detail, grid and contours grey; red pecked British front line, and German trenches and trench names. Overprint in dark blue: Positions Map, positions active and positions inactive between 1-1-18 & 7-2-18., Used by Major J. C. Thomson, OC 20th Siege Battery. WW1 Trench Map Collection: Box PC14, Envelope 390.