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Pre-20th-Century cannon projectiles are my specialty-area of relic study. Because literally multi-millions of iron/steel balls have been manufactured which are NOT artillery projectiles, you'll need to clean
all of the rust-encrustation off of two spots on opposite sides of that ball, and measure it super-precisely with Digital Calipers. If its "cleaned" diameter fails to match up
exactly with any of the well-documented diameters of Historical Grapeshot (or Canister-shot) balls, it is not an artillery projectile.
The following link will take you to a set of charts telling the exact diameter of Cannonballs, Grapeshot-balls and Canister-balls used in America from the Colonial era through the Civil War era.
www.civilwarartillery.com/shottables.htm