A video of what is claimed to be a prototype version of a 64GB iPhone 4 has emerged online.

M.I.C. Gadget claims that the device is very similar to the iPhone 4 prototype that Gizmodo got its hands on last year.

Similarities between the two devices include a lack of plus or minus signs on the volume controls and a missing silver ring around the camera lens.

According to the website the phone is not hacked and runs iOS 4.1. In the two minute video (below), which at the time of writing had only been watched 300 times, the device's storage capacity is shown to be 59.1GB.

On the back of the unit, you can see 'XX GB' where the storage capacity would normally be shown.

The owner of the prototype apparently told M.I.C. Gadget that he acquired it from a source who has access to a number of these devices, which were leaked from Foxconn’s factory in Shenzhen.

It looks to all intents and purposes like an iPhone 4, though is bound to spark speculation about whether the next-generation iPhone will offer a 64GB capacity.

The most recent rumours about the forthcoming iPhone 5 suggest that Apple will revert to an aluminium back for the device, dropping the glass back used in the iPhone 4 due to concerns over weight, paint thickness and scratching.