Hi squarepants, and welcome to AF
The Note II uses a micro SIM, so unfortunately it sounds likely that it's a fake.
However, there was this one odd story:
Samsung makes a Galaxy Note II with both micro and regular SIM card slots official in China. So if it has both regular and micro slots it's perhaps possible you got one of those?
Can you give us any other information about it? Software info is good - baseband is something they don't normally fake, for example.