Digging around and turned up this little bit @ Barron's
The factory floor in Fort Worth is considered by Moto to be very state of the art. Each assembly line can switch over from making the stock black or white models of Moto X to the custom units with a flick of the switch that directs workers to pick the custom parts from the right bin — a system known in the trade as “pick to light,” because a bank of lights directs the worker where to reach for parts. It takes about 2 hours to assemble a custom phone, a Motorola employee told me. At the end of assembly, a computer system scans the assembled unit to make sure the colors and the stenciled message match exactly what the customer ordered.
"Assembled by USA Workers"