Although IMEI numbers can only strictly indicate the amount of iPhones produced, rather than sold, the Cross estimate may in fact be pessimistic, as it assumes that 1.5 million phones were unsold -- whether defective, sitting in stock or in use as demonstration models.

If accurate the figure would easily put Apple over its sales target for the year, 10 million, and beat out predictions from industry analysts. Consensus views have generally forecast 4 million phones for Q4, while Piper Jaffray has suggested as much as 5 million. A definite figure may only become available later this month, when Apple formally announces its Q4 results.