"We have seen a significant uptake in demand for silver in recent days, both for coins and for 1,000 ounce bars," Mark O'Byrne, research director of bullion dealer GoldCore, said.
"Silver Maples are being snapped up by U.S. and Asian buyers as the premiums are lower than for silver Eagles. Silver Philharmonics continue to be popular in Europe as they too are cheaper than Eagles, with a similar premium to Maples."
Gold and silver Philharmonics are issued by the Austrian Mint, while the U.S. Mint issues American Eagle coins.
Demand for silver coins and bars accounted for more than a fifth of total demand in 2013, according to a report by the Silver Institute.
An ounce of gold is now about equal in price to 74 ounces of silver, the biggest spread between them since early 2009. Due to its greater affordability, silver sales tend to outstrip gold in volume terms and attract a lot more retail buyers.
"Supply of silver from some mints has been delayed," said Brian Lan, managing director of Singapore-based retailer GoldSilver Central.
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"Demand had not been great early this year, so they had reduced production capacity and manpower. When there was a spike, they were caught off guard," Lan said.
Most mints across the globe typically launch a new product lineup at the beginning of each year. They would not be sitting on big inventories towards the end of the year, and a ramp-up in production could take a while.
In September the Royal Canadian Mint started allocating, an industry term meaning rationing, its Maple Leaf silver coins in response to high demand, according to a spokesman.
With the allocation of silver coins in place, the mint continues to produce and take orders for 2014 coins with no anticipated halt in shipments, he said.
But retailers are already finding it hard to get hold of the mint's products as they sell out their existing stock.
"The premiums of silver Maple Leaf bullion are going to rise soon, because dealers cannot get their hands on the coins," said Scott Spitzer, chief operating officer at Manfra Tordella & Brookes, one of the largest U.S. coin wholesalers in New York.
Some Asian dealers said they had to pull Maple Leaf coins from their lineup until they get the mint's 2015 products.
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American Silver Eagles
In mid-April 2013, silver lost nearly a fifth of its value in two days, tracking a rout in gold, which prompted a rush to snap up both the metals at bargain prices.
But with the drop to four-year lows last week, demand for the two metals this time around has not been the same.
Demand for gold has picked up in Europe and the United States, but in Asia, the top gold-consuming region, the sort of buying frenzy that occurred last year has not taken place.
"(Silver) supply is not as bad as April 2013, but there is definitely more tightness in the chain," said Gregor Gregersen, a director at Singapore retailer Silver Bullion, adding that supply times were increasing.
The U.S. Mint is not allocating silver or gold at the moment. In June, the mint lifted a rationing of silver American Eagle coins that had been in place since January last year.
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The U.S. Mint sold 1.4 million ounces of silver American Eagle coins on Friday alone, the highest daily sales since the new 2014-dated coins first became available on Jan. 13.
The Perth Mint, which runs the only gold refinery in No. 2 gold producer Australia, said it was not facing any supply issues. It usually launches a new line of products from September, unlike the other mints.
"We built up a lot of stock for those releases. So we have quite a few months worth of stock," said Neil Vance, wholesale manager at the Perth Mint.
"If this had been a different time of the year, it would have been a different story."