75 Xbox One Prototypes
100 Kinect Prototypes
200 Gamepad Protypes
Gadget design is rarely a simple process, and we now know that the Xbox One is no exception to the rule. Microsoft designer Carl Ledbetter has revealed that the game console went through many 3D-printed incarnations before the company settled on a final product; there were 75 system prototypes, 100 for the Kinect and 200 for the gamepad. The development team spent a long time finding a balance between familiar Xbox design cues and the desire for an always-on media hub, Ledbetter says. Whether or not you think Microsoft achieved its goal, it's clear that the Xbox One's current look was never guaranteed.
Source: http://www.engadget.com/2014/01/20/microsoft-discusses-xbox-one-prototypes/?icid=maing-grid7%7Cmain5%7Cdl26%7Csec1_lnk3%26pLid%3D432558