Plate 4 was registered on 19 May 1840. This plate is sometimes refereed to as the "Spotted Plate." Since this plate, like Plate 3, has very few characteristics to aid in identification, one must use the process of elimination.  Plate 4 does not have Ray Flaws or the O Flaw, nor does it have the bulge on the bottom frame on each side of the O of One.  This means the elimination of Plates 1a, 1b, 2, 7, 8, 9, 10, and 11 and leaves  only Plates 3, 4  and 6.   Plate 3 does not have the characteristic of many dots and therefore can also be eliminated.  This leaves only Plate 4 and 6 which both have characteristic dots.  One means of eliminating Plate 6 is if  it has a black Maltese Cross, since Plate 4 was destroyed before the black Maltese Cross came into use.   Plate 4 stamps as a rule have more dots than plate 6, and Plate 6 has more ragged side frame lines.  However, the safest means of differentiating Plate 4 and 6 is to take measurement of the check letters using the The Plating of the Penny 1840-1864, Volume 1.
 
 
 

EG	AC	TK

Example of dots in check letter square (enlarged and indicated in red)