20.O27 [Cambrelin Wood and Trench, South of Nachtegaal] December 10, 1917
Covers an area equivalent to portions of squares O27, 32, and 33 on the corresponding WWI map sheet 20. Negative roll 9B, photo 114. Annotations on recto: north arrow pointing to the upper-right with an "x" on the opposite edge of the photo. WWI Aerial Photograph Collection: Box 1, Envelope 13.