According to RBI statistics, there were 64 thousands million pieces of banknote in circulation as on March 31, 2011. It means that in every million, there were 6.74 forged notes detected.
To help people identify duplicate currency notes, RBI has come up with a new knowledge base website Pehchano Paise Ki Boli, Kyunki Paisa Bolta Hai.
PaisaBoltaHai explains the ways one can detect counterfeit notes. Visual presentations of notes of 10, 20, 50, 100, 500 and 1000 rupee denominations of Mahatma Gandhi series are available on the site. You may download the posters of these and a documentary film is also there.
The description about bank notes focuses on some points which can be experienced by visually challenged people, like the portrait of Mahatma Gandhi, the RBI seal, promise clause, Governor's signature are done with intaglio print which can be felt by touch.