The 'P' stamped on the dime is the sigla for Philadelphia Mint.
The definition of sigla are abbreviations or symbols with written meaning which are used in a book and typically explained at the beginning of the book.
An example of an abbreviation in the sigla would be U.S. which stands for the United States.
plural nounsing. sig′lum
abbreviations, symbols, etc. used in the scholarly edition of a text as to indicate manuscript sources
- plural form of siglum