Series Number Id: UNKNOWN. Sheet number: part of sheet 27. In black overprint: Secret, [Second] Army Railways 6-18 [June 1918]. "[4th] Field Survey Coy., R.E. (8731) 30-4-18 [followed with black overprint] (9161c) 16-6-18". "Reference" with railway details also in black overprint. Grey detail and squaring; relief-layered in tints of buff (brownish-yellow colour)., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC19; envelope_number: 576.