Seen on YouTube, the legendary 3rd generation iPod touch with a camera. This is probably one of the most common prototypes, for a good reason: the decision to abandon the camera came quite late in development.
The video is interesting as it highlights Apple’s design flaws. First, the centered camera is generally a bad idea, never replicated—there’s a high risk of users accidentally covering the lens with their fingers. Second, DongleBookPro explains that the cable placement likely required manual assembly, which is problematic for mass production. The flex cable had to be routed between other cables. And third, though I disagree, he argues that the hardware platform wasn’t powerful enough to handle it. This reasoning is odd—the device had a SoC equivalent to the iPhone 3GS, which managed its camera just fine. Even the iPod nano had a camera that worked reasonably well.
As he explains, the few somewhat functional prototypes are very poor—the image is often flipped, chromatic aberrations are numerous, etc. Clearly, the sensor wasn’t very effective, that’s obvious. In practice, it wasn’t until the 4th generation iPod touch that an iPod touch with a camera was released.