How do you determine where your coin came from?

If you mean where it was minted, this is generally shown by a "mint mark".

If you mean what country it came from, the easiest way to tell is to look for the name of the country, which will probably be on the coin somewhere. It may not be easy to read, since it will probably be in the language of that country rather than in English, and may not even be in the Latin alphabet.