Series Number Id: UNKNOWN. Sheet number: part of sheet 51. Secret First Army railway map, May 1918. Black overprint at head of map: "Secret"; "Railways 15-5-18." Includes "Reference" to normal gauge, light railways and metre gauge. "[First] Field Survey Co., R.E. 6063." Grey detail and squaring., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC14; envelope_number: 385.
