Per the following, it is my understanding that while there was consistency/uniformity in the look of the flags, there was some slight differences in material, edge coloring (orange, white), how stars, andrews cross, etc located, designed and such (2nd issue, vs 3rd issue, etc).
JIM T

The Union troops of the East saw uniform flags starting in late November, 1861 when the first silk ANV flags were issued. As the Richmond Depot began making more wool bunting flags and more units got them then the uniformity got even more uniform so to speak. However, it was not really until after the Gettysburg campaign that the ANV was fully equipped with their flags due to bunting shortages.