Hold on to your hats, folks. A video of what appears to be the next iPhone's rear plate has emerged. And get this: The company that posted the video was hawking the part for $700 – but now it's sold out.

Mobile phone parts seller ETrade Supply published a video Wednesday showing what could be the backplate of the next iPhone. The part in the video matches up with other purported leaked images of the next iPhone's backplate.

The design of the purported iPhone 5 part also supports one of the most widely circulated rumors concerning Apple's next smartphone – namely, that the phone will feature a larger 4-inch display and a slightly elongated form factor relative to that of the iPhone 4S, Apple's current flagship phone.

Still, it's important to remember that although this part exists (at least in a single video), and backs up rumors and reports, it's not necessarily the real deal.

"It’s entirely possible that what someone captures might indeed come from Apple or a supplier. But it might also just be a branch of design that’s going to be pruned rather than make it into an actual product," Gartner analyst Charles Golvin told Wired. "Apple does lots of different designs and mock-ups, most of which do not make it to the final product."

The part in the video could also just be the product of an individual or company with the means to mock up and manufacture a realistic-looking, Apple-branded part.

ETrade Supply, the source of today's video, is a "multinational retailer of phone parts products and services," according to its website, where it offers parts like the Apple iPad Digitizer Touch Screen Frame and iPhone 4S LCD screen. ETrade Supply sells similar parts for a wide array of handset and tablet models from different manufacturers.

Most curiously, under the Apple product section of its site, ETrade Supply also offers three products under the "iPhone 5" category: a home screen button, a SIM card tray, and an "OEM Apple iPhone 5 Rear Housing" listed for $700, but tagged with a red "Out of stock" notification.

A request for comment from ETrade Supply was not immediately answered.

Apple CEO Tim Cook recently said that Apple would be "doubling down" on secrecy, and Golvin notes that's not just for Apple employees, but applies to Apple suppliers as well. "They’re held to very stringent requirements in terms of protecting the work that they do for Apple, and from things being released out into the wild," Golvin said.

But the closer we get to an actual product launch, the higher the likelihood that "leaked parts" could be genuine articles – simply because of the sheer number of parts being manufactured at that point. With the iPhone rumored to be released for a fall launch, there could be some design wiggle room yet.

via 9to5 Mac