I'm not familiar with the tool that you mentioned, but Cr-48 was the very first Chromebook. You're correct that it wasn't available for retail, however it was distributed publicly for evaluation purposes in anticipation of the next round of Chromebooks a few months later. I guess one could call it brutalist in its design - no frills and designed to put the "browser as the OS" concept front-and-center without distractions. The full line-up can be seen here:
https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/