Without knowing more about the stamp, it's impossible to answer. You need to include the country, date (if you can find it) and what is on the stamp (who or what is on it). Also a rough idea about the cindition would help in pricing the stamp.
To many variables. You need to fully identify the stamp you are interested in, some things to figure out: What was the country of issue? Was the stamp canceled in 1913? or does it commemorate something that was made in 1913 and has that date in the design? What condition is the stamp in? Is the stamp used or look like it just came from the post office? Consult a stamp catalog online or at your local library.
1-4$
Too many variables. You need to fully identify the stamp you are interested in, some things to figure out: What was the country of issue? Was the stamp canceled in 1913? or does it commemorate something that was made in 1913 and has that date in the design? What condition is the stamp in? Is the stamp used or look like it just came from the post office? Consult a stamp catalog online or at your local library.
One 20th of a dollar
In circulated condition, about 3 cents.
In average circulated condition, value is 50 cents to $2.00
I can find no reference to a "unique" 1913 Penny from any country.
There's no coin called a "buffalo penny". Indian head cents were made from 1859 to 1909, and buffalo nickels were made from 1913 to 1938.
In order to give an accurate estimate, the coin should be seen. I suggest you take it to a coin dealer and have it appraised.
There has been talk of eliminating the US penny for many years. Before they switched from the bronze alloy penny to the copper clad zinc penny it cost about 3 cents to mint every penny. Even the copper clad zinc penny costs more than a penny to mint. Of all standard issue US coinage only the nickel (5¢) and the penny cost more than their face value to mint.
Penny Illustrated Paper ended in 1913.
There is no such coin. Buffalo NICKELS were first released in 1913. No 1-cent coin has ever carried a buffalo image.