The Reserve Bank of India was established under the aegis of the Reserve Bank of India Act, 1934 [Interesting fact: Section 1 came into force on 6 March 1934; Sections 2 to 19, 47, 50 to 52, 55 to 58 and 61 were brought into force on 1 January, 1935 through the notification in the Gazette of India, 1934, Pt. I, p. 1369, and the other sections were notified on 1 April 1935 in the Gazette of India, 1935, Pt. I, p. 538.). In other words, the Reserve Bank of India became fully functional in 1935.
This being the case, in 2010, the Reserve Bank of India or "RBI" as its commonly called, celebrated its 75th year of operation. In other words - the 'Platinum Jubilee'.
To commemorate, the Government of India issued a set of five commemorative coins in the denominations of Re. 1, Rs. 2, Rs. 5, Rs. 10 and Rs. 75 to mark the occasion. While a gazette notification in respect of these coins has already been issued on 23 February, 2010 in Official Gazette of India, Prime Minister Shri Man Mohan Singh will release the coin in an official function at NCPA, Nariman Point, Mumbai in a Grand Finale event to mark end of Platinum Jubilee celebrations. The RBI describes the coins in detail in its press release, which can be accessed here.
I happened to get my hands on a Rs. 10 coin (and a Re. 1 coin that I showcase here), which has a bi-metallic design, as you can see in the photos below:
The coin in the photograph is actually a circulation coin with a Noida mint (evident from the 'dot' motif below the inscription of the Platinum Jubilee years 1935-2010).
As you can see, the outer ring has a copper tone comprising mostly of copper and aluminium and nickel to a smaller extent. The centre piece has a more silver tone, which is a blend of copper and nickel.
This lot of commemorative coins was officially launched and released by the then Prime Minister of India, Shri Man Mohan Singh at an official function at NCPA, Nariman Point, Mumbai in a grand event to mark end of the RBI's Platinum Jubilee celebrations.