How old is your Scotch? Ask a scientist.

Alarmed by the rising amount of counterfeit antique Scotch whisky circulating worldwide, industry experts have turned to carbon dating to verify age, London's Daily Telegraph reports.

In one case, a 1856 bottle of Macallan Rare Reserve, expected to sell for $30,000, was withdrawn from auction after tests showed it dated from 1950.

When they get a suspicious bottle, officials at the Edinburgh-based Scotch Whisky Research Institute send samples to the Oxford Radiocarbon Accelerator Unit.

There, it's tested for carbon-14, a naturally occurring radioactive isotope that begins decaying when a plant or animal dies. Paleontologists use this method to date organic samples.

From that, the age of the barley used to make the Scotch can be determined.

Whiskies bottled after the early 1950s are even easier to spot: Nuclear tests raised the level of carbon-14 in the atmosphere, giving those samples a unique signature.

"So far there have probably been more fakes among the samples we've tested than real examples of old whisky," an accelerator lab official told the Telegraph.

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