Piedfort Coins

A Piedfort or piedforte (misspelled as piefort in the influential Krause and Mishler Standard Catalog of World Coins), is a coin often exactly twice its  normal specifications like weight and thickness. The name is derived from a French word , meaning "heavy foot". They are normally not circulated, and only struck for presentation purposes by mint officials for collectors or VIPs or available in Proof set of Coins.
Great Britain's Royal Mint is well known for creating many commemorative piedfort coins, especially since the 1980s.

Not many such kind of coins have been minted in India.
As per Standard Catalog of World Coins , Krause Publicaiton only one such coin was minted in India, whose detail are as follow :

KM# 277  -- 100 RUPEES
29.1600 gm, 0.9250 Silver 0.8672 oz.
ASW Series: International Year of the Child 
Obv: Asoka lion pedestal, denomination below
Rev: Native musicians and dancer

Minted in year 1981 as Proof Coin by Mumbai Mint.