Series Number Id: GSGS 2742; Sheet number: 57c SE; Edition number: 6f (local), Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC09; envelope_number: 229, Manuscript: sound-ranging base with numbered microphone positions 1-6 in area west of Peizieres - west of Metz-en-Couture, in blue crayon; also more forward base in red crayon; for location of German artillery before the attack on the Hindenburg Line (final advance).