It could be like a calendar thing or something that required them to stick something to the black area of the actual thing (eg rip off calendar, notepad). Or something to your school to say thank you and they just sent a blank one by mistake lol. I dunno *shrugs*
Aren't you supposed to stick post-its on it? Looks like it could be for that?
Heat it up and see if any magical markings appear on it...
First reaction is that it's meant for a phone or PDA or something similar to be displayed on it.