In 1961, the Republic of China (Taiwan) issued a souvenir sheet celebrating the 1st anniversary of President Chiang Kai-shek's 3rd inauguration (Scott #1319a). Given the number of issues honoring Chiang Kai-shek, it would seem that the citizens of the R.O.C. were most grateful for the many years of their paternal dictator's leadership. 100,000 were issued, and Scott '12 values the unused souvenir sheet at $20.00.
Better stamps and souvenir sheets of the R.O.C. have done well over the last few decades, but the market has been cooler than that for stamps of the People's Republic. I believe that as capitalism and incremental democratization take hold in the P.R.C., relations between the "two Chinas" will gradually improve, as will demand for stamps of the R.O.C.. The process of thawing may have already begun: as of 2008, more than $ 150 billion has been invested in the P.R.C. by Taiwanese companies, and about 10% of the Taiwanese labor force works in the P.R.C., often to run their own businesses.
In the meantime, most of the demand for stamps of Taiwan will originate from collectors in Taiwan itself and among overseas Chinese (of which there are approximately 35 million). Taiwan, a nation of 23 million people, is one of the four "Asian Tigers," and has experienced explosive economic growth and industrialization over the last 5 decades. Annual GDP growth has averaged about 4% over the last 5 years, but this reflects the zero growth of 2009, a result of the global financial mess.
Those interested in learning more about investing in stamps are encouraged to read the Philatelic Investment Guide ($5), available on Kindle, and accessible from any computer.