Cant find any reference to this here …looks like a fascinating new addition to Google earth;

http://news.ebrandz.com/google/2010/3124-google-earth-demonstrates-historical-aerial-images-of-world-war-ii.html

“To see the pictures, download Google Earth and click the clock icon in the upper status bar.”
I opened my GE, clicked the clock icon and switched to Aug 1950 –
great vintage map from the nearby city Dortmund or the old airfield of Duesseldorf – really fascinating!