Military History/Brass Ball
Found this Brass Ball digging a basement in the Oshkosh Wisconsin area. Measure 3.75-3.85 has a .25 hole in it that has some faint threads. There is something in side as you can shake it and feel it moving. Seems soft as you do not get a hard sound when shaking it. Quite heavy maybe 8-10lbs
The ball is most likely part of some ornamentation. I've gotten a lot of questions about similar objects where people purchased them thinking they were cannon balls. Brass was never used for cannon balls, cannon barrels, yes, but not the projectiles. Brass is too soft, and too expensive. Iron was used for the projectiles.
The closest shot diameter to your object was the 6lb cannon shot, it was 3.58 inches in diameter. As to what might be inside, probably soil if the object was buried, or left over sand from the casting method used to make it.
The fuse plug on a hollow cannon ball, what was called a "shell" would have been about an inch in diameter to take either a wooden fuse plug or a threaded one.