Emailed on March 22, 2019 in The Friday Forward

For 2.5 years before its release, Apple had developed the iPhone in secret. So secret, that engineers developing the different components weren't even able to see how they interacted with each other. 

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 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. The Verge has obtained exclusive access to the original iPhone M68 prototype board from 2006 / 2007, thanks to Red M Sixty, a source that asked to remain anonymous. It’s the first time this board has been pictured publicly, and it provides a rare historical look at an important part of computing history, showing how Apple developed the original iPhone.

Picture below, but the article is worth the read here.