Macotakara points to a blog post [Google translation] from case design firm MGM showing off a new case intended to fit Apple's rumored lower-cost iPhone. The photos reveal a case that is largely identical to iPhone 5 cases, with the exception of being approximately 2 mm thicker.
iPhone 5 case (left) vs. lower-cost iPhone case (right)
Macotakara has also posted a hands-on video of the case. In the video, an iPhone 5 is placed into the case and appears to fit fairly well. It is clear, however, that the case is intended for a device with rounded edges rather than the squared edges of the iPhone 5.
Descriptions of the lower-cost iPhone having curved rear edges date back to a January report from iLounge that suggested the device would adopt curvature similar to the iPod classic, while appearing as a cross between the iPhone 5 and fifth-generation iPod touch in other respects.
Apple's lower-cost iPhone is expected to be introduced in the September timeframe and has been rumored to be including a number of color options in order to help differentiate the device from Apple's main iPhone line.
Case designs have accurately hinted at Apple's design plans a number of times in the past, although case makers have on occasion been fooled as was seen in 2011.