Sometimes the type is not so obvious, and you'll have to consult a guidebook or a collector familiar with that state to find out what it is. In my opinion, international plates are the most interesting plates to collect. There is virtually no end to the variety of plates to be found, and many countries can be obtained surprisingly cheaply. The only way to really judge the value of international plates is to look around at what other collectors are selling them for, or better yet ask an experienced collector. Many tourists bring home plates as souvenirs, and plate collectors get plates while traveling.
Some countries are very strict about turning in expired plates.
Even though they have many cars, plates from Greece, Italy, and Japan are not that easy to get. For instance in countries with Communist governments, the passenger plate can sometimes be a rare type, because most vehicles are government-owned. Also, plates with graphics such as flags or outlines of the country naturally tend to be more desired by collectors. But sometimes the plainest looking plates can be the most valued by the experienced collector. For the benefit of the newer collector, I have listed some of the easier to get international plates.