Why Indian coins have certain symbols like dot,star,diamond.

The coins have certain symbols so that that can be identified where they have been minted.                                                                

Coins that don't have any symbol's.                If you have seen these coins, understand that they have been minted in Kolkata mint. The Kolkata mint was established in the year 1757.                                                            

Coins with diamond , 'B' or 'M' symbols below the year.                                                   It means they have been minted in Mumbai mint. The Mumbai mint was established in the year 1829.                                                     

Coins with a star, split diamond or dot in diamond symbols.                                             it means that they are from Hyderabad mint. The mint was set up in the year 1903 by the then government of the Nizam, Hyderabad.                                                         

Coins with round dot symbol.                         it means these coins have been minted in Noida mint, established in the year 1984.