It kinda-sorta looks like it has a fuzeplug but its diameter-to-weight ration proves beyond any doubt that it is a Solid (not hollow) ball. In this case, what looks like a fuzeplug is either an actual iron plug or a casting mold's vent-hole projection.
Unfortunately Cletus's info for diameter and weight is too imprecise for me to say whether the ball is a cannonball or not.
Here's a link to an educational article I co-wrote about how to tell with CERTAINTY whether a ball is an Artillery ball or not, incluing helpful instructions and photos. For example, it shows a Diameter-Tape (a.k.a. Pi Tape) and how to use one ACCURATELY on a ball.
SolidShotEssentialsMod
Doing the "Pi" math (9.5" circumference divided by 3.1416), the ball is about 3.02-inches in diameter, and is reported to weigh "just under 4 pounds." According to the US 1861 Ordnance Manual's cannonball diameter-&-weight charts (
www.civilwarartillery.com/shottables.htm) there was a RevWar 4-Pounder caliber Solid-Shot cannonball that weighed 4 pounds 1 ounce and was 3.12-inches in diameter. So, the not-very-precise report from Cletus indicates this ball is a little too small and too light to be a cannonball. Might want to borrow a Digital Caliper to do the precise diameter measuring that is need. Also, please weigh it on a precision scale, such as a Postal Shipping scale, and then report the very-precise diameter and weight info to us.