Could it be a Logitech keyboard? (Logitech has its own protocol that needs a micro USB connector)
This is what the features page says:
Works with USB keyboards.
Use the on-screen keyboard, an alphanumeric keypad, or attach your wired or wireless USB keyboard for easy text input. Perfect for searching videos on YouTube or updating your status on Facebook.
I use a Logitech K260 that included a mouse and USB dongle. It’s 2.4ghz so there COULD be problems with wifi networks. I haven’t seen any problems with mine though.
I have used two differerent Logitech Keyboards so far and both worked fine. As flhthemi, I am currently using a K260 that also has a mouse and no issues at all. Keyboard works on everything it should and mouse shows up when using the “Browser trick”.