ALL cannonballs had to be very carefully manufactured to be perfectly-round, so they would not jam inside the cannon's barrel during firing -- which could cause the cannon itself to burst. So, the Army and Navy Ordnance Department had Inspectors, whose job was to use a ring-gauge to check every cannonball for perfect roundness (and exact size) before the ball was issued to the artillerymen. Any "lumpiness" would make the ball be rejected by the Ordnance Inspector and be sent back to the foundry to be melted down and re-cast.
Note that the ring-gauge's center is a PERFECT circle. Placing it around the ball and rolling the ball would detect any out-of-roundness or "bumps" on the ball's surface. This example has a marking of “8.77” which would have been used to inspect 9” mortar rounds. Wonderful piece of Civil War artillery history!
Inventory Number: ART 288 / Sold