This link may help to identify some of the varieties:
http://www.linncopex.com/Flag%20on%20Pole.htmRemember, the stamps were printed by various printers (Ashton Potter, Sennett and Avery Dennison) so varieties were inevitable. Further, some were gummed and others were self-stick stamps.
There's also a note in the Scott Specialized Catalog that as it relates to the PSA coils, Scott 4132-4134 are on backing paper as high as the stamp, whereas Scott 4135 is on backing paper that is larger than the stamp.