Series Number Id: UNKNOWN. Sheet number: part of sheet 28. "Secret Army administrative situation map 1-2-18" in black overprint. "[Fourth] Field Survey Coy. R.E. (8039) 29-12-17 [numbers crossed out and replaced with black overprint] (8217)." Grey detail base map, with purple grid letters and numbers. Covers all of Ypres Salient, from Merckem in the north to Armentières in the south and Menin in the east; Ypres is in left centre. "Reference" shows railways, tramways, ammunition and other railheads, army roads, water points, ammunition and supply refilling points, and more. Railways in black; army roads in red., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC27; envelope_number: 789.