bullets ww2

This is a WW2 all brass, 3" Mark ii M2 artillery shell casing dated 1944. I can't find another anywhere on the web that matches. I paid $20 for it with intentions to sell but unless it is worth quit a bit i believe i'll hang on to it. Opinions on value?

I bought this brass casing that had been sold at a scrap yard. Any help on the value would be greatly appreciated.

Found these in Sicily Italy while freediving around cliffs in Cassibile. WW2 battle sight (according to locals) with a concrete gun turret up the beach North about a half mile. Found them underneath the water half buried in sand between rocks about 5 feet below the surface of the water.