If you look at the EXIF data of this picture taken by an Apple employee, you will see that it was taken by an iPhone 4, but the rest of the information doesn't match with the any of the current iPhone models:
"This (very attractive) photo claims to have been taken by an iPhone 4, but the rest of its EXIF data tells a different story: although the image has been cropped to 2235x2291 (5.12 megapixels), the original picture was a much larger 3264x2448 -- or just shy of eight megapixels. What's more, the lens was recorded as a 4.3mm f/2.4, which is closer to that of a point-and-shoot than the iPhone 4's actual 3.85mm f/2.8."
Here is some of the EXIF data:
Via MacRumors
