In 2007, India issued a souvenir sheet commemorating the Centennial of Mahatma Gandhi's Non-violent Resistance, or Satyagraha, Movement (Scott #2208e). 200,000 were issued, and Scott '12 prices the unused souvenir sheet at $3.00 .
While the quantity issued may seem high compared to those of most stamps recommended by StampSelector, it should be kept in mind that India is a rapidly developing nation of over a billion people, and millions of Indian collectors will probably be converted to the insidious cult of Philately over the next decade.
As for the sheet's topical appeal, it couldn't be any stronger, as many Indians view the Mahatma as something like a semi-divine combination of Jesus, Washington, and Lincoln. Gandhi Topicals with low or moderately low printings, whether from India or elsewhere, are worthy of consideration as investments.
Those interested in viewing a list of scarce stamps with printing quantities of 100,000 or fewer may wish to view the StampSelector Scarce Stamp Quantities Issued List, which currently contains over 9,700 entries. Researching quantities issued data is vital to determining in which stamps to invest.
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.