The Verge:

Apple had developed the iPhone in secret over those two and a half years, and for many inside the company, the device had only been known by the codenames “M68” and “Purple 2.” Apple was focused on surprising everyone with the iPhone, and that meant that many of the engineers working on the original handset didn’t even know what it would eventually look like.

To achieve that level of secrecy, Apple created special prototype development boards that contained nearly all of the iPhone’s parts, spread out across a large circuit board.

I knew this was one of the ways Apple showed the protoype iPhones but it’s the first image I’ve seen of it.