The Philadelphia CDS cancel is a significant aid in dating and colorizing the 1851-57 3-cent George Washington imperforate stamp of the United States. The ink used in Philadelphia for canceling devices was changed abruptly from blue to black in early 1854, with January 14th, 1854 being the earliest known use for the black Philadelphia CDS. Since the claret, brownish carmine, and yellow brown stamp colors were in use during two different distinct periods in the life of the issue, those bearing Philadelphia CDS cancels can be dated to one period or the other. Identification of stamp colors and plate wear can help further define dates of use.
The below images illustrate the evolution of the Philadelphia CDS cancel and the colors of the 3-cent stamp.