On pages 18-19 of the January 2015 Bulletin (No. 185) Barry Friedman illustrates Indian "censor handstamps" on 1924 and 1936 covers. These are forgeries made, probably in the early 1980s, to dress up the faulty (and therefore otherwise unsalable) covers of the "Chettiar correspondence" (actually several correspondences from and to various chettiars, merchants, in India and Malaya). I have seen, additionally, forgeries of airmail and railway markings. Some of these "censor handstamps" are close copies of legitimate WWII markings, and some are completely novel designs. Some even appear on WWII mail and are, in those cases, dangerous.
Konrad Morenweiser has an Appendix dealing with these in his Zivilzensur in Britisch Indien 1939-1945 (1985).
When looking at Indian censored covers, if you have an inter-war faulty Chettiar cover, its "censor handstamps" are certainly forgeries. If, however, you find something censored from the Northwest Frontier in 1930-31, gently put it in a sleeve, look up "Red Shirt Rebellion" and write a nice little article for the CCSG Bulletin. In the 1990s John Hardies showed me such a cover and I pooh-poohed it. When he later showed me the regulation allowing censorship in response to this uprising, the Red Shirt Rebellion became for me the Red Face Rebellion.