A good friend of mine from the Houston area (I live in the Beaumont, TX area) had a G-g-grandfather that was the 1st sgt. of Co. E. (Ambrose Edwards) He, too, was captured at Gettysburg and spent the remainder of the war at Ft. Delaware. (my g-g-grandfather was Green Brown. He enlisted in March of 1862 and served throughout the Shenandoah Valley campaign. He was discharged just before Cedar Mountain for phthisis pulmanalis. We would call that "tuberculosis" these days. The flag the 15th carried at Gettysburg survived the war, only to be buried with the flag bearer (John Archibald) in Eufala, AL, sometime after the war. We can't say with absolute certainty what type it was, but the odds are in favor of it being a 3rd bunting issue type. Basically 48" +/- square, 5" bars w/ thirteen 3-1/2" stars spaced at 6" apart and a white border. The quintessential ANV battle flag.