The most obvious  means of  distinguishing  between the  issues of 1899,   1900 and  1901-02  is  the  date  or  lack of   it, on  the  shield. But frequently the date is very difficult    to read.    In such cases  these several   issues may be distinguished by less obvious
differences.    The principal differences in design of these three issues are indicated below:

Issue of 1899: Date,   1899,  on shield;   letters and figures of labels more  than 2.5mm tall;   28 rays  in left panel;  rays  touch lower  corners of  left panel;  9 rays  touch semi-circle  above shield; the words "UNITED" and  "STATES"  touch  third ray and end on seventh ray; period after “STATES.”

Issue of 1900: Date,  1900, on shield;  letters and figures of labels  smaller   than in preceding issue,  being  about  2mm tall; 28 rays in left panel;  rays do not touch lower comers of    left panel;  10 rays touch semi-circle above shield; “UNITED” does not  touch third ray and extends beyond seventh ray;  "STATES" touches both  third and eight  rays;  no period after "STATES". 

Issue of 1901-02: No date on shield,  letters and figures of labels smaller than in eithar of  the two preceding  issues, being about 2mm tall;   30 rays  in left panel;   11 rays   touch  semi-circle above shield.

Tha  last series of  SELLO stamps was  issued  in 1903,  at some  time subsequent    to March. 15th.    Dr.  Perry, writing under the date of March 15,   1903,  stated that new plates were being prepared for engraved stamps  at that time. Forbin has erroneously listed this  issue as released in 1902.    The  issue of  1903 consisted of only three denominations: 25c,   50c,   and 1p.    It appears  to have been printed from  plates produced by photographic process which produced a background of dots. The design is of  the same  type as the three preceding  issues,  but the upper  label  reads "CLASS"  followed by a number.    This  issue remained in use until  the  supply was exhausted about the  end of 1904.

CUSTOMS  stamps which began to be issued in 1902 replaced SELLO stamps on customs documents.  And subsequent  to  January  1,   1905, DOCUENTARY stamps replaced SELLO stamps on other documents which had required SELLO stamps prior to that date.