Series Number Id: GSGS 3458. Sheet number: part of Sheet 36. Battles of Vimy Ridge and Arras, First Army situation map 10 April 1917. "Ordnance Survey, March, 1917." Detail, contours and squaring grey. Overprint in blue: First Army Front, Situation at 4.0 p.m. 10/4/17; shows original Front Line pecked blue, Advanced Line (on east slope of Hill 145 and Vimy Ridge) solid blue line, patrols (east of Farbus) large blue dots. Also in blue overprint: 1st Field Survey Co., R.E. 2066., WW1 Trench Map Collection: Box PC16, Envelope 446.