Analysts looking at both Apple's results and those posted by AT&T - Apple's iPhone partner in the US - have noticed a large discrepancy in the figures.

Apple says it has sold 3.7m iPhones in total. AT&T says it has sold 2m iPhones, and European operators are believed to have sold between 300,000 and 400,000 handsets.

Which means there are either 1.3m iPhones being used as bookends, or an awful lot of people have gone to the trouble of unlocking the devices to run them on different networks.

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Analyst Toni Sacconaghi of Bernstein Wealth Management believes the figures are high enough to suggest both a sizeable market for unlocked phones and a build-up of iPhone inventory - unsold phones. Unlocked phones would hit Apple revenues - the company gets a cut of monthly revenue from its network partners. But excessive inventory is expensive too.

In presumably related news, Digitimes reports Apple is cutting orders for iPhones for the second quarter from 2m to 1.1-1.2m handsets due to lower-than-expected demand in Europe.

However, at the company's most recent analysts conference, Apple executives re-iterated that they expect to sell 10m iPhones by the handset's first birthday, in June.

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