Second-hand Nexus 5 owner discovers test build of Key Lime Pie running on device

We often hear the classic story of people ending up with a prototype of a device after a night at the bar. This time, it was literally given straight to the customer.
When a brand new Nexus 5 owner turned on his device, he discovered it was actually running a test build of Key Lime Pie instead of 4.4 KitKat.
He got the device second-hand, and after trying it out a bit, he found that the build was not stable was continuously crashing. After some investigating, he found the screen above.
Nothing too exciting was on the device or too different from the regular build other than a few hidden menus.
This happens every once in a while, but the devices are updated to the most recent version of Android when they’re turned on. However, such as with this case, test builds don’t get OTA updates, so the customer had to flash KitKat.
Source: AndroidAndMe