In a magazine article I read about that all coins minted in India have a symbol below the year of issue indicated which mint they got produced. As per RBI website here, coins are produced in mints across four cities in India, they are India Government Mints at Mumbai, Alipore (Kolkata), Saifabad & Cherlapally (Hyderabad), and Noida (UP). This wikipedia article says the symbols that correspond to each city’s mint.
- Mumbai: diamond
- Kolkata: no mark
- Hyderabad: star
- Noida: dot
I took few coins and checked on this, was a good time pass with my son today.