Cannon ball or navigator ball or shot put

[eagleeye911]

We have recovered some navigator balls or kelvin balls in our area, but never come across one this big with such a small mounting hole. Sorry in advance for the photos, as we haven't had eyes on it yet. Apparently the only anomaly is the small hole, which is threaded. The embossed marking seems to read, "D, 5, 56". It is reported to be approximately 6 inches in diameter and weighs 17.2 pounds.

 

[US-Subs]

Looks like a shot put. I get about one every couple months "donated" for the collection.

 

[John D. Bartleson Jr.]

Eagleeye is that a scredw-in plug next to the small hole? Normally a shot put has a threaded plug that can be removed to add or remove lead pellets to bring it up to proper weight.
The small threaded hole should not be there if a shot put.
Phone your high school track coack and ask him about the diameter and weight. Also shot puts are usually made of brass.
It could also be a counter weight for a gate closure; a finial for a fence or gate post,etc.
Regards,
John