Powder Keg,
It's possible that the Drawing was for this gun. Pate, Tappey & Lumsden
Made in 1861, 3.13 cal., 70" oal. cyl. 13.5 and a 48"smoothbore barrel. It is outside the Center Hill Mansion. The other one blew up in trials.
CW,
The 2 barreled cannon is in Athens ,Ga. Got some pictures of it last spring. A neat freak gun.
If I new how to size pictures I would try and post one.