Unidentified photographer (15 Sq. Photo-Section) 1918 (ca) Shows present condition of Central Albert, ruined Cathedral and buildings in vicinity. W28 Map 57d
Stereoview Ebay (Ralph Reiley, pers. Email, 28 November 2022) I think all these photos are for training purposes, probably just after WW1.
(Ralph Reiley, Facebook comment - Photohistory Quest - "795. Stereographs as aerial photography training aids", 30 November 2022) I have found what W28 is. It is a grid on Map 57D. The British made a grid of the parts of Belgium and France that was their part of the Western Front. Each grid had a number. 57D was the area where the city of Albert France was, it was in grid W in square 28.
