The global market is growing for rare banknotes in good condition, said Jared Stapleton, director at Toronto Coin Expo, Canada’s premier coin and banknote show. “Even though the world’s economy is in a state of uncertainty, rare banknotes are still selling for top dollar,” he said.

In the Indian market, some of the hardest to find, and most valuable, currency notes are those that were printed during the French, Portuguese and British rules in India. Also rare and sought-after are the rupee bills that the Government of India issued in 1959 for exclusive use in the Persian Gulf countries by the Haj pilgrims from India. “These notes were issued only once,” said Razack and can now command as much as $30,000, for a 100 rupee bill on the open market. “The most remarkable feature is the colour of these notes, which is different from the existing notes in circulation in India at the time. The colour differentiation was to identify that these notes were not considered legal tender in India.”

Most coveted

John Millensted, currency specialist at the British auction house Bonhams, said the rarest pieces tend to be specimens or trial pieces which aren’t necessarily taken up as a design for a banknote. “Most banknotes with over 40 years of age hold their value,” he said.

Sometimes it’s the simplest notes that can become most collectable. For example, a £1 ($1.44) note from World War I with an overprint in Arabic, used by British forces in Turkey in 1915, can fetch up to £8,000 ($11,549), even though the note is quite plain, Millensted said.