This is a special version of Xbox 360 Fat console known as "Demo kit" Fat version.

These specific consoles were given to media and developers. They were also used at various EXPOs such as "Igromir" in Russia. They were mainly used to demonstrate early versions of the games to the public or for debugging purposes. Some small dev studios had these consoles too.

You can tell that it is a Demo kit by looking at the sticker at the back of a console. If I am not mistaken, early Demo kits always had white shells and "Demo kit" label.

Usually they were Xenons and Zephyrs, but there are also Demo kits in Elite shells with Jasper motherboards with no "Demo kit" label attached to them.

It is also known that in the early days Microsoft re-purposed beta kits and made Demo kits from them.

Demo kits are technically developments kits with an "xShell", but never with a Sidecar. Demo kit looks like a regular console and it doesn't say anywhere that it is a XDK, which they are. Some consoles have black unique labels. Shipped in a brown box.

With this type of a console, users were not able to play retail games, only dev signed and prepared discs/builds.