Thats what Im going on.
Orders for Raid by 'B' Coy, North of the FERME DU BOIS, on the night of the 26th/27th inst (Feb 1917)
Reference Map - RICHEBOURG. 36.5W3, 1/10,000
Point of entry - 5.16a.85/10
Think the clues there are Richebourg(Obviously) and its based on a 1/10'000 scale map. The point of entry, I think, refers to a trench sector.