"Looks like the 99th Illinois Flag, that was captured on May 22nd, 1863 at Vicksburg. Color-Bearer, Thomas H. Higgen's continued on with the flag, while the regiment fell back. Around 100 Confederates aimed at Higgin's and fired, but not a shot hit him. He was later waved into the defensive works and was actually applauded by the Confederates who witnessed his bravery. The 2nd Texas Infantry was in that area and may have captured the flag."
The flag in question in the original post was that captured at the Railroad Redoubt in the area of the siege line defended by Gen. Stephen D. Lee's Alabamians, Stevenson's Division."
The flag described by Corporal Higgins of the 99th Illinois was captured, along with himself, by men of the 42nd Alabama and 2nd Texas, Forney's Division, defending the rifle-pits, just southwest of the 2nd Texas Lunette and northeast, about 300 yards of the Railroad Redoubt.
The flag of the 18th Indiana was planted in the ditches fronting the 2nd Texas Lunette by Sgt. Francis M. Foss. The literature does not indicate if this flag was recovered or later captured.
Bearss, pp. 828/9