An U.S. company has introduced a small counterfeit bill detector designed for retail use that can sniff out the "super dollar," a convincing yet bogus US$100 bill allegedly produced in North Korea.

At five inches wide, three inches tall and six inches long, the D500 Super Dollar Authenticator is diminutive enough for retailers to place beside cash registers, said Carlos-Andres Gonzalez, a vice president of sales for AccuBanker USA.

The D500 is one of many fake currency detectors on the market from different vendors. The U.S. Treasury department has warned that counterfeiting operations are increasing since lesser-skilled criminals can make better fakes with today's PCs and digital printers.

Detecting counterfeit bills often isn't easy by eye. A bogus $100 bill Gonzalez had on hand -- believed to have been made in North Korea -- would be nearly impossible for a novice to finger as a fake.

The paper it is printed on contains no starch and doesn't reflect ultraviolet light, which is one sign of a fake. It has the security strip on the left side of the bill and a watermark of Ben Franklin -- whose portrait is on the bill -- on the right-hand side, as well as replicating other security features.

AccuBanker's scanner looks at several aspects of the bill to confirm its legitimacy, Gonzalez said. U.S. paper money is printed with magnetic ink, but that's also used for many fraudulent bills. But on real bills, the ink is distributed in a consistent pattern whose magnetic resonance can be mapped.

The magnetic map is stored in the D500, as well as three other maps containing ultraviolet, infrared and other measurements taken from legitimate bills, Gonzalez said, at the Cebit show in Hanover, Germany. Scanning a bill takes less than one second.

"If there's any spike, any anomaly in any of the threads of data, then it rejects that and says 'Hey there's something suspect,'" Gonzalez said.

It's up to the retailer how they want to handle a situation where they believe a counterfeit bill is being passed, Gonzalez said. But if the fake bill is detected by a bank, it's the retailer's loss.

At the end of 2005, the U.S. Secret Service estimated $61 million of the $760 billion in U.S. money circulating worldwide was fake.

AccuBanker sells the D500 for $199, and it can also be converted to accommodate different currencies.