Steam Box tester and YouTube user Corey Nelson released a video of himself unboxing the console prototype.
The system, packaged in a simple brown crate, comes with the beta controller, manuals, HDMI and USB cables, a power cord, a wi-fi antenna and a recovery USB key. You can watch the video above for a look at its contents.
Valve announced in September that it would ship prototypes to 300 testers; machines were sent out last week. Shipments were timed with the beta release of SteamOS, Valve's Linux-based operating system, that launched on Friday.
Steam Machines, SteamOS and the Steam Controller are expected to launch in 2014.