The base is all banged up, you can see that in the picture that shows a view from the bottom. Its possible it was made that way, but to me it looks damaged. This bronze is hollow I think. I believe it has a clay core. The base may have originally had a bronze surface on the bottom, and that part has been broken and is now gone. Or not, but you can plainly see the exposed clay down there, so that makes sense to me.
I thought all bronze sculptures were hollow, except for very very small ones? Thats what I've read on all the websites I've researched.