The artifact was in fact a Panama mount, 'gun turret,' installed in 1942 in a sub-post of Fort Moultrie known as Marshall Reservation during WWII.

SULLIVAN’S ISLAND, S.C. (WCSC) - The Fort Moultrie Post Theatre is a landmark on Sullivan’s Island, and its history dates back to 1930. It’s now up for preliminary approval for its next use at a ...

Fredericksburg, Fort Moultrie, Devils Postpile National Monument ...