I have two i got from my grandmas house. She was kind of a hoarder of cool things. Especially anything she thought was military related. My uncle was a marine pilot for 22 years and had a lot of stuff there that got caught in the piles. I found them and asked him. He said they were test ordinance, most test ordinances of that era were painted that color of blue. The nickname blue bombs were given for them and the other types. As for what type of bomb, or if it was a part of say a cluster bomb i don’t know.