There is a way to determine with CERTAINTY whether an iron ball is an Artillery ball or one of the many versions of civilian-usage imposters, We American cannonballs collectors rely on the historical Artillery ball diameter and weight measurement data in the US Ordnance Manual of 1861. The can view the size data charts for cannon balls, Grapeshot balls, and Canister-ammo balls here:
www.civilwarartillery.com/shottables.htm
But for those super-precise diameter and weight charts to be useful, you must first knock off as much of the thick dirt/rust encrustation on your ball. Then, use a caliper or a diameter-tape to PRECISELY measure your ball's diameter (in inches, not mm). Then, weigh the ball on a super-precise scale, such as a Postal Shipping scale -- because typical household bathroom scales are notoriously inaccurate.
Then, after you've obtained your ball's VERY-EXACT diameter and weight, look for an extremely close match-up for it in the Ordnance Manual's Shot Table's charts. For example, you said your ball is about 10-inches in diameter. The Shot Tables say a 10"-caliber Solid Shot (not a hollow shell) cannonball was precisely 9.87-inches in diameter, and weighed 127.5 pounds. A 10"-caliber cannon Roundshell was the same diameter and weighed 101.67 pounds. A 10"-caliber Mortar Shell was the same diameter and weighed 88.42 pounds.
Your photo of your thickly-encrusted ball seems to show two holes going deep into its interior. Is that correct? If so, it's not a cannonball or Mortar ball. Both of those types had a single fuzehole, about 1.25-inches in diameter, and the Mortar ball had a smaller "notch" on each side of the fusehole (a total of two notches), for using tongs to load the ball into the mortar. The photo attached below shows civil war yankee artillerymen using tongs to carry and load the ball into the mortar, on Morris Island during the siege of Charleston SC in 1864.
When you've removed all the rust-encrustation you can, and you've precisely measured and weighed the ball, let us know the result. I'm hoping it really is a 10"-caliber cannonball -- but only the precise diameter and weight measurements can tell us for sure, yes or no.