It seems to me reading your post and looking at the MOC Collection that there were a number of unidentified 2nd Nationals which were picked up when they captured the 7000+ on April 6, 1865. It appears that at least on the surface that the Eastern Confederacy (ANV) was begining to use 2nd Nationals more later in the War than the Western Army of the AoT as actual "battle flags". I know that you see the AoT use these flags more or less as battleflags, while the ANV seem to use them more for Headquarter or Post/Battery identification purposes.