“The Baltimore Battery”

September Formed in Virginia.
Jackson’s Valley campaign
September 17
Battle of Sharpsburg (Antietam)

The battery was commanded by Captain John Bowyer Brockenbrough. It was  armed at Antietam with four guns of different types: a 3 inch Ordnance Rifle, a 12-pounder Blakely Rifle, a 10-pounder Parrott Rifle, and a 12-pounder smoothbore howitzer

From the monument and marker on the Antietam battlefield:

The Battery, under the command of Capt. J.B. Brockenbrough, occupied a position near this marker at daybreak, and opened the battle on the Confederate side. 

 The Baltimore Battery (Confederate) fired from this spot into the Union forces in the Cornfield. It included a 12 pounder iron howitzer (like the small gun before you), the only one of its kind among the 500 cannon at Antietam

assigned to Stuart’s Horse Atillery
 July 1-3
Battle of Gettysburg

Commanded by Captain William H. Griffin, it brought four 10-pounder Parrotts to the field,