The three basic 3c types differ in the configuration of the outer framelines. Type I, with the frameline complete all around, was issued both imperforate and perforated from nine plates. The Type I stamp was the first to be issued with perforations, beginning in February 1857. Types II and IIa were printed from twenty plates and issued only with perforations. On both types the framelines at top and bottom have been removed—the side framelines are continuous on Type II and broken between stamps on Type IIa. 28 of the 29 plates used to print 3c stamps were numbered (1-28), and one of the plates that produced only imperforate stamps was not numbered (Plate O).
Although these plates produced a multitude of varieties, surpassing even the 1c stamp, the Scott classification of 3c stamps is restricted to colors of the imperforate (Orange Brown, Scott 10, or various Red shades of Scott 11) and types of the perforated (Types I, II and IIa, Scott 25, 26 and 26a, respectively). There are differences other than color that distinguish Orange Brown printings from other shades, such as the presence or absence of recut lines within the design.
Most of our knowledge of this complex stamp originates with Dr. Carroll Chase, who published his first book on the 3c 1851-57 Issue in 1929 (revised in 1942). The Chase book is still regarded as the definitive work on the subject, although other students of the issue have augmented his plating and color studies. Dr. Chase’s personal collection of the 3c 1851-57 was dispersed many years ago.