Any idea on how many bombs might have been dropped during that time frame? My guess is certainly hundreds of thousands.
Something like 20% of the bombs dropped by the USAAF in Europe were duds.
This should be able to give you an answer, http://afhra.maxwell.af.mil/aafsd/aafsd_index_table.html
RAF Scampton had a live Grand Slam bomb (22,000lb) as a gate guardian.Apparently when Lincolnshire County Council were widening the road past RAF Scampton's main gate in about 1958, the 'gate guards' there had to be moved to make way for the new carriageway. Scampton was the WWII home of 617 Sqn, and said "gate guards" were a Lancaster...and a Grand Slam bomb.When they went to lift the Grand Slam, thought for years to just be an empty casing, with an RAF 8 Ton Coles Crane, it wouldn't budge. "Oh, it must be filled with concrete" they said. Then somebody had a horrible thought .... No!..... Couldn't be? ... Not after all these years out here open to the public to climb over and be photographed sitting astride! .... Could it? .... Then everyone raced off to get the Station ARMO. He carefully scraped off many layers of paint and gingerly unscrewed the base plate.Yes, you guessed it, live 1944 explosive filling! The beast was very gently lifted onto an RAF 'Queen Mary' low loader, using a much larger civvy crane (I often wonder what, if anything, they told the crane driver), then driven slowly under massive police escort to the coastal experimental range at Shoeburyness. There it was rigged for demolition, and when it 'high ordered', it proved in no uncertain terms to anyone within a ten mile radius that the filling was still very much alive!Exhaustive investigations then took place, but nobody could find the long-gone 1944, 1945 or 1946 records which might have shown how a live 22,000 lb bomb became a gate guard for nearly the next decade and a half. Some safety distance calculations were done, however, about the effect of a Grand Slam detonating at ground level in the open. Apart from the entire RAF Station, most of the northern part of the City of Lincoln, including Lincoln Cathedral, which dates back to 1250, would have been flattened. http://www.gunnies.pac.com.au/gallery/grand_slam.htm