Found for about $6 CAD. I ended up grabbing it out of curiosity for the weird dials, numerous macro keys, and the Microsoft Sidewinder branding.
Sidewinder was Microsoft’s pre-XBox, “extreme” gaming-oriented peripheral brand, and they slapped the name onto various input devices. The Wikipedia article on Sidewinder goes into some detail on the history, cancellation, resurrection and re-cancellation of the brand. Some of the controller designs are pretty out-there. This keyboard hails from around 2008.
The Sidewinder X6 has a column of macro keys along the left side, a bunch of macro keys above the Funtion Key row, and two curious dials on the top-right. The underlying mechanism is a rubber dome membrane. To use the macro keys, you need to install Microsoft’s Mouse and Keyboard Center software.
So, why two dials? One is for volume, and the other… drum roll … dims the red and amber lighting beneath the keys.
(Re: the brighter light coming from the ‘S’ key: somebody scraped away the paint on that key for whatever reason.)
Where’s the number pad? The number pad is a separate component that can be connected to either the left or right side of the keyboard. I like the idea of a modular keyboard, but the downside is that the components can be lost: the unit I found didn’t come with this proprietary attachment.
I don’t really have a use for the macro keys, but gimmicks aside, it’s a decent backup USB keyboard. One person on Amazon really didn’t like the placement of the Esc key (on standard layouts it appears above tilde (~), but on the X6 it’s over further to the left).