I've sent this info to Scott as a PM, but others might find it of interest. This picture was in an article on air power in the December 1, 1941 issue of Life Magazine on page 97. The caption identifies it as a B-17B. Here is a link to this Life Magazine issue via Google Books magazines.
https://books.google.com/books?id=X04EA ... &q&f=falseOn page 9 of this issue under "Life's Cover", this is part of the caption under the cover picture:
"This particular plane is a B-7B, recently overhauled to increase armor-plate protection for pilots and crew. Leak proof gas tanks have also been installed, firepower made heavier and more effective. With it's four 1000 h.p. Wright engines, it makes close to 300 mph."