Slant 6 Head: metal rod in heads water jacket?

So... I just found it curious that there is an "almost floating" metal rod in the head. I mean it can't go anywhere, but it's "loose". Doesn't look like something that could have been put in there AFTER manufacturing, so I'm guessing it's a byproduct of the casting process? May it held something in place while the head was cast? Or??

slant6head_metalrod.jpg