The bulk of the story is a flashback to WWII, but the absence of the gang members of that era (e.g., Gorcey, Jordan, Benedict), as well as the presence of Clements and others who weren't members back then, goes unexplained.
In a scene set during World War II, one of the Bowery Boys is reading a comic book published in 1957.
At the beginning of the film, the man from the government states he's from the War Department. That agency was replaced by the Department of Defense ten years previously in 1947.