Even if it is just a rock, it is a very cool rock that I would have loved as a kid. 

Good point!

Diameter?

If it's metal, it's likely a canonball.  If it's stone, it's a cool rock.     (Maybe it's a ball bearing for a main battle tank sized monster truck.  The key to its identity is likely its origin ~ where it was originally found).

Garden ornament.

I happened to come into possession of a stone that someone thought looked interesting and I agree it is very odd if it was naturally formed. Can anyone help me tell what it is/ when it was made or if it is just a cool rock. Any opinions would be helpful!

Welcome neighbor!

I joined a little bit ago, but haven't really done anything at all. Just consider this the first time I really have been on here. Been on the US Militaria Forum since September. 

Thanks..... The link is in the blurry picture that you cannot read unfortunately... It is from a USGI who landed in anzio in 1944 The same year the flak unit was transferred to Italy.   ... I have his scrapbook with a bunch of newspaper cuttings and some letters back to his parents... He was in Italy the same time this flak unit was ... All the plates came from the same gi's estate.... I don't know where he obtained the other two plates...

From the U.K.? British?   Close look at post #4, I am ten thousand percent sure that what you have is a really cool piece of shrapnel from a No. 36 Mills Bomb.   https://en.m.wikipedia.org/wiki/Mills_bomb  

Here are some brighter and better photos. I haven’t taken it out of its display case but thanks for the tip!

A few other photos