India, Oct. 26 -- It has been 15 years since the 25p coin went out of circulation. While it was still in business, it was the face of a structural anomaly that prevailed in the Indian coinage system. In the 1970s, the 25p coin was 19mm in diameter, making it smaller than the 26mm 10p coins of the time. The 10p coins, in fact, were larger than the 24mm 50p coins too. In 1982, a new series of 10p coins measuring 23mm in diameter was issued, followed by smaller versions. But the 25p anomaly remained until the coin was phased out in 2011.

With paise coins no longer in circulation, rupee coins being used today by and large follow a simple relation between size and denomination: a larger coin usually means a higher value. The only departure fr...