what is this? (pic included)

[patey]

well,it has no writing on it,it vaguely looks like a micro sd card but my phone doesnt detect an sd card installed. it could be a sim card but i'm not sure as i currently dont have a contract. when i bought the phone it did have a contract (i bought this phone from kijiji) but i had the contract cancelled. there are no gold pins or anything on the card but there is a sort of spot that looks like a computer chip for the phone to read it. doesnt make much sense to me any ideas?

and i must say,wonderful response time and very nice people