https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/samsung-sandy-bridge After some further searching, I found that this model has a physical “Dev Switch” located on the right side by the power button. Similar to how a paperclip hole below the power button invokes recovery mode, the Dev switch is responsible for invoking Developer Mode. The switch was switched “on” or to the right, and I was able to use a small flathead to switch to the left (off.)
