Check out these china prototype manufacturing images:
Black-backed early prototype
Image by jimabeles
This is a really early 2G prototype. Unlike my other prototype with the silver back (and a couple others that have surfaced on the web), the case is all black. And the screen is a matte, plastic material.
Unlike the other prototype, which boots to the iPhone OS, this one only boots to the diagnostic program.
The serial number indicates that it was manufactured in in China, the 42nd week of 2006 (the iPhone was announced the 1st week of 2007 and released June 29, 2007).