What type of shell is this, and is it dangerous?

I have a shell in my shed, (Just the projectile part) I found in the gutter when I was a kid. It's a 75mm shell, if I remember right. It's shaped like a rifle bullet. It's about 10 inches long. The bottom part is steel, the top part looks like aluminium, but has a plastic-like feel to it, so I assume it's supposed to deform and set off some explosive. OR, it's just a model. The bottom part has the remains of blue paint on it, which I assume means it was either used as a door-stop, or the color is to signify either what type of shell it is, or whether it's live or not.