It is part of the postal savings system of India Post.
These can be purchased from any Post Office in India by an adult (either in his/her own name or on behalf of a minor), a minor, a trust, and two adults jointly.
These are issued for five year maturity and can be pledged to banks as collateral for availing loans.
[1][2] Other similar government savings schemes in India include: Public Provident Fund (PPF), Post Office Fixed Deposit, Post Office Recurring Deposit, etc.
[3] The certificates were heavily promoted by the Indian government in the 1950s after India's independence, to collect funds for nation-building As of April 2016, Ministry of Finance enabled purchasing and redeeming of these bonds in electronic form and financial institutions no longer issue a physical pre-printed certificate.