Apple has limited iPhone Duo order quantities to a maximum of 2 per person in several countries including the United States and Britain. Delivery dates were pushed back to January next year within minutes of pre-orders opening, a move seen as aimed at blocking bulk purchases for resale.

NineToFiveMac reported on Oct. 20 that Apple online stores in the United States, Britain, Japan and Spain display a notice about purchase limits when customers add more than 2 iPhone Duo devices to their cart. The same limit applies regardless of configuration.

The move appears intended to respond to limited initial supply and the spread of reselling. Dozens of iPhone Duo listings have already appeared on online secondhand marketplace eBay, and some prices topped $5,000 (about 6.6 million won). The aim is to reduce the practice of buying large quantities of scarce devices and reselling them at prices above the retail price.

This is not the first time Apple has limited purchases of supply-constrained iPhones. In China, it has previously applied limits not only to online orders but also to in-store purchases. Apple also took the same step in the United States when it launched the iPhone 5 in 2012.

Purchase limits alone may not be enough to eradicate organised reselling. Reseller groups may try to buy in bulk by using multiple virtual card numbers, email addresses and shipping destinations to bypass limits, or by having other people place orders on their behalf. Apple may also take separate, undisclosed steps to detect and block such purchase attempts.

Some consumers said they saw changes indicating delivery dates were brought forward. After iPhone Duo delivery schedules were delayed, estimated delivery dates improved for some orders. Apple has not disclosed specific reasons for the delivery schedule adjustments.

How long the purchase limits will remain in place has not been confirmed. Apple is using limits to deter bulk buying aimed at securing early launch supplies and to respond to reselling problems involving supply-constrained new products.