It was indeed a Second National. There is an article about the color bearer having a replica flag made after the war which remained in his family into the 20th Century. I have copies of that article and they depict a Second National.

The 18th Mississippi Cavalry Battalion also got a Second National which was hoisted over Ft. Pillow and then captured at Brice's Crossroads in June, 1864.

Both units should have also received Mobile Depot flags.

Greg Biggs