Does unsweetened chocolate go bad?

I just found some Baker's unsweetened chocolate squares in my pantry, and I was going to make brownies with it. Once I had all the ingredients, I got out the chocolate and looked at the sell by date and it was August 2010. It looks fine, dark and smooth. I smelled it, and it smells fine, but I haven't smelled unsweetened chocolate before so I'm not really sure how its supposed to smell. I would really like to know if I should still use it or trash it. Thanks so much!