During the six decades of Indian independence, four mints have been operating in India: Kolkata (Calcutta), Mumbai (Bombay), Hyderabad and Noida.
The four mints of the republic of India (click image to enlarge).
The plants at Kolkata, Mumbai and Hyderabad were already operating when India gained independence in 1947. The establishment of the Noida mint was sanctioned by the government of India in January 1986 (source).
During the reign of Edward VII (1901-1910), when Kolkata was the capital of India, coins minted at Kolkata bore no indication of their mint of origin, while coins minted at Mumbai were marked with a small B for Bombay. This system was retained during the reigns of George V (1910-1936) and George VI (1936-1947), although the B for Bombay was substituted by a bead, dot or diamond in various positions. (There are a few exceptions to this rule, but we cannot go into details with this subject here). During the second world war a mint at Lahore was also employed. This mint was initially designated by a small L, though this was soon substituted by other markings. During the colonial era, the mint at Hyderabad produced its distinctive coinage for the kingdom of Hyderabad.
When India attained independence in 1947, Pakistan was established as a separate state, while inheriting the Lahore mint from the British. The state of India was reorganized into a federal republic, incorporating in the process a large number of princely states, which had been an integral part of the British colonial system. Thus, the mint of Hyderabad was incorporated into the system of mints administered by the central government of India.
The mint marks of the years immediately preceding independence were also applied after 1947. Thus, the coins of the Kolkata mint have no mint mark, while the coins of the Mumbai mint carry a diamond. The Hyderabad mint was designated by three different successive mint marks: vertically split diamond (1953-1960), incuse dot in diamond (1960-1968) and star (since 1963) (all dates according to the SCWC 2007, p. 987). The Noida mint, established in the 1980ies, is designated by a round dot.
The four mint marks used by the mints of India from the 1970ies to the present. From left to right: Kolkata (no mint mark), Mumbai (diamond), Hyderabad (star), Noida (dot). (Click image to enlarge).
Apart from the four mints of the Republic of India, a number of foreign mints have produced coins for India, namely Ottawa, Birmingham, Kremnica, London, Mexico City, Pretoria, Moscow and Taegu. The Mumbai mint has issued special coins in proof condition for collectors. These may carry a B (for Bombay) or M (for Mumbai) mint mark instead of the usual diamond.
The home pages of the Indian mints can be found here:
Kolkata: http://igmint.org/
Mumbai: http://www.mumbaimint.org/index.html
Noida: http://www.noidamint.org/index.htm
Apparently, Hyderabad mint does not have a home page of its own.
See also "Modern Mints of India" by Roger deWardt Lane.
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Added July 9th 2007:
The Kolkata and Mumbai mints have been minting coins continuously throughout the era of Indian independence, while the establishment of the Noida mint was sanctioned by the government of India only in 1986, as stated above.
In Hyderabad, only 1 pice/paisa coins were minted during the 1950ies, adding the 3, 5 and 10 paise denominations to the production range in the 1960ies, and broadening the scope further since about 1970. Many of the Hyderabad issues of the 1950ies and 1960ies appear to be minted in small quantity. Thus, the Hyderabad mint only gradually became a regular mint alongside the others.
The foreign mints that have produced coins for India are listed below, together with the specific coins minted (according to the listings in SCWC 2007):
Ottawa: 10 p. 1988, 25 p. 1985, 1988, 50 p. 1988.
Birmingham: 1 r. 1985.
Kremnica: 1 r. 1998, 1999, 2000.
London: 1 r. 1985, 2 r. 1999.
Mexico City: 1 r. 1997, 5 r. 1999.
Pretoria: 1 r. 1998, 1999, 2 r. 1998.
Moscow: 2 r. 2000, 5 r. 1999, 2000.
Taegu: 50 p. 1985, 2 r. 1997, 1998.
At the point in time when the authorities initially resorted to supply from foreign mints, the existing mints were incapable of fulfilling the demand for small change. The Noida mint was established in an attempt to solve this problem (source).
