Sources pointed out that while the impure coins minted at Calcutta have only 8 per cent of silver, stocks being dumped by Surat-based parties contain 40 per cent silver, Mumbai-based ones have 35 per cent purity and stocks from Delhi have about 50 per cent silver.

These coins are minted in varying sizes and weights of 20g, 25g, 10g and 5g. Care is taken to see that the coin's dimensions match those of pure ones to ensure a normal course of transaction, sources said.

Market sources claim that since Diwali is considered auspicious for purchasing coins with images of gods and godesses, and with the price of silver zooming, these unscrupulous elementshave dumped impure stocks which are being passed off as 99.5 per cent pure silver coins.

These coins have no resale value as the silver content is highly negligible. However, these coins are sold at a discount to buyers paying in cash by some parties in Mumbai and elsewhere. Market estimates put the annual sale of these coins at 200 tonnes all over the country.

These traders are also helped by the prevailing religious myth that silver coins bearing images of lord Ganesh and goddess Laxmi should not be sold or melted. However, psychiatrist Manish Kaushik says that the myth could have been spread by the trade itself to increase the consumption of coins.

Due to such beliefs, the number of coins reentering the market for melting is a bare 3 per cent to 5 per cent little and the owners never find out that the coin in their possession is impure having no resale value.

This has also hit trading at 15 to 20 major showrooms as they are unable to compete with the lower rates at which the impure coins are beingsold.

These shops normally sell branded coins minted by reputed references like National Refinery, Narandas Manordas and RR Jain, who are in the buisness since 1965.

These coins are also used as gifts on auspicious occasions and many buyers intending to gift them away fall prey to the lower rates at which the impure coins are being sold.

Sources cited an example of a business journalist who attempted to sell a small stock of such coins mainly received by him as gifts during various press conferences. Of about three dozen coins, he was informed that only about half a dozen had resale value.

According to the Bombay Bullion Association president Makhanlal Damani the only way to avoid being duped is to buy coins from reputed shops and insist for a bill of purchase indicating the purity.

Chances of the reputed brand names being fakes are less if the showrooms are selling it under a valid invoice indicating purity. This helps the buyer verify the purity even if he does not intend to sell it back tomarket, bullion analyst Madhusudan Daga said.