20.O28 [Houthulst Forest, Southeast of Nachtegaal] December 10, 1917
Covers an area equivalent to portions of squares O28, 29, 34, and 35 on the corresponding WWI map sheet 20. Negative roll 9B, photo 144. 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 20.