Series Number Id: GSGS 2551a. Strategical map. "Ordnance Survey, 1916." Grey and blue outline map, showing rivers, international boundaries, and double and single railways. Map covers whole zone of Western Front (SE England, Holland, NW France and Belgian Coast, Switzerland and W Germany)., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC20; envelope_number: 624.