During the past 150 years, multi-MILLIONS of round (and "round-ish") metal balls have been have been manufactured for civilian purposes, having nothing to do with artillery. Some examples are:
Mining-&-Stonemilling Industry rock-pulverizer balls ("Mill-balls"),
large ball-bearings,
sports Shot-Put balls,
ornamental-ironwork balls (such as a gatepost-top),
and even cement-delivery truck tank-cleaner balls.
Therefore, we cannonball collectors needed a way to tell with CERTAINTY whether an "old-looking" metal ball is an artillery ball or a civilian-usage ball. So, to give our fellow collectors (and the public) the needed information, historian David Poche and I co-wrote an extensive education article with detailed instructions (and photos). You can read it online, for free, at:
SolidShotEssentialsMod
Extremely-precise weight and diameter measurements for cannonballs, Grapeshot balls, and Canister-ammo balls used in the US and Canada from the Revolutionary War through the Civil War can be viewed online, for free, at:
www.civilwarartillery.com/shottables.htm
BigJT, I see your info-request is your very first post here. Welcome to TreasureNet's "What Is It?" forum, the best place on the internet to get unknown objects CORRECTLY identified.