Does anyone know the difference between the Dominica 1963-67 14c Type I (Scott 171) and Type II (Scott 171a) variants? My Googling has failed to find an answer. I did find one seller on eBay, wacl2, offering both variants (here), but I honestly can't tell the difference, even in the zoomed-in images: StampWorld shows variants for several values (4c, 6c, 8c, 10c, and 14c) in this definitive series (here) but without explanation. Colnect does not specify variants (which it normally does if they exist). Help!