The decimal system of 100 Paise to 1 Rupee was introduced on April 1st 1957. The Rupee remained at the same value but was just differently divided. The word "NEW" preceded the word Paisa and Paise for the first seven years of this system, though this word never appeared on the coins in English. This wording on new coins was changed and the Hindi word for "New" dropped as from the introduction of 1964 dated coins on June 1st 1964.
 

From then on the Republic of India series developed further and further. The Hyderabad mint began to make large quantities of most of the coins, as well as the mints at Bombay and Calcutta. For some unbeknown reason the list of denominations issued became about as long as any other I know of. There were 1, 2, 3, 5, 10, 20, 25 and 50 Paise and 1 Rupee coins, though of course some denominations were less popular than others. The shape, flan-size and composition of very few of these denominations remained constant. For example there are five different shape/flan-size/composition combinations for the 10 Paise coins.

(I will sometime get an image done to show - the five different guises of the 10 Paise coin.)

In the 1970's it became a regular thing for circulating commemorative coins to be introduced each year for a few denominations. Each year a different design based upon a different theme was chosen for this purpose. These designs were usually welfare, environment or anniversary related. These coins would often be produced in similar numbers to the standard design pieces of the relevant denominations. High denomination pieces in Silver were also produced for collectors with these designs. Coins of 1, 2 and 3 Paise all ceased to be struck for circulation during the 1970's. At the other end of the scale the 1980's saw the introduction of 2 and 5 Rupee denominations, though these earlier pieces saw only limited circulation. Towards the end of the 1980's the 10, 25 and 50 Paise coins changed to smaller steel coins. These steel pieces were among the first coins to be made by the new Indian mint at Noida, which is near New Delhi and always uses a round dot as a mint mark. The 1990's saw the eventual demise of the 5 Paise denomination, the change to steel for 1 Rupee coins, the introduction of a smaller 2 Rupees coin, and that of a small, thick 5 Rupees coin. In recent years all three of the main denominations i.e. 1, 2 and 5 Rupees and to a lesser extent the 50 Paise denomination have been used additionally for circulating commemorative designs with more than one such design for some years. This all adds up to a lot of coins, even if I omitted to mention that distinct die varieties exist for many types and occasionally (in 1985, 1988 and in the last several years) foreign mints have been used for a few denominations.

(Here I plan to have an image of each of the 5 denominations currently in proper use in India - perhaps I will use just 2000 dated pieces - though I have not yet heard of a 5 Rupees for 2000 yet.)