The post was seen in the forum of WeiPhone.com. Assuming it is an actual part, it would appear to be from a prototype since it is missing the typical labeling you would see on a production version.
9to5Mac spoke to iDeviceGuys, an iPhone and iPad repair shop, who told them that the SIM card slot appears slightly smaller than the microSIM used in the iPhone 4S. The connection points are also closer together. That may - or may not - point to the iPhone 5 using the so-called new nanoSIM format that it was rumored to embrace.
The images don't show off the iPhone 5's processor, however. While a quad-core processor has been rumored, so has a tweaked A5 processor that's been called the A5-2.
In addition, iDeviceGuys said that the battery connector for the iPhone 5 has five pins, compared to four on the iPhone 4S. Images purporting to show the iPhone 5's new battery recently leaked. If valid, they show the iPhone 5 getting only a 10mAh bump in capacity, although it also gets a bump in voltage, to 3.8 volts.
It's widely expected that the iPhone 5 will be the first iPhone to support LTE (in fact, if it isn't Apple will be harangued); iDeviceGuys added that the motherboard shows more antenna connections (compared to the 4S), which may - or may not - mean that the device supports LTE.
The digitizer connector for the display also appears modified, which may point to the already-rumored in-cell touch panels that Apple is rumored to be using in the iPhone 5 (the in-cell touch panels will enable the device to have a thinner screen).
None of this will be confirmed until Sept. 12, when Apple will launch the iPhone 5. Of course, that date is also yet another rumor.