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So this was a real mystery in a plastic bag.

http://imgur.com/a/dbYmJ

I've taken the best pictures I could with my crappy camera and then glare-reduced them in Photoshop (hence, the halo effect, sorry) - basically, the only idea I have about this mouse is that it might be Bluetooth. It came with exactly what you see in the pictures - minus the battery. There was no receiver that came with them.

I've tried doing the Bluetooth pairing in both Windows 8.1 and 10, and neither operating system sees it. I've tried switching the on-off switch while Windows is searching, I've tried switching the on-off switch holding down the DPI button while Windows is searching, I've tried spam clicking the hell out of it while Windows is searching - nothing seems to get this mouse on Windows' radar. (Bluetooth was already previously turned on in Windows to pair an Android phone, so that is not a problem). I've tried following the instructions on Microsoft's site but the mouse has no "pair" button. When I turn it on the internal camera just blinks red and turns off.

So if anyone has any insight into this - who made it (possibly a user's manual somewhere?), how to get it working, anything that can help me figure this one out - it would be greatly appreciated.

Even if you don't think your response might be helpful - if you have any ideas whatsoever, it might be helpful.

Did you check under the battery cover? I know Logitech and Microsoft wireless mice tend to put their USB receivers in there.

At first, I replied that there was nothing inside the battery covers. But then I noticed something odd - there was a little box thing that seemed a bit out of place. You were right - that was a USB receiver. Thank you Wildweasel!

Awesome, I'm glad I could be of help.