What is a value of a 1964 Electric Gibson SG Special with Gibson Case?

There are too many variables in order to give the value of ANY guitar sight unseen. The best thing that you can do is to find a guitar that is closest to what you are questioning at an online auction site and see how much it sells for. If there is not one being auctioned that is close to the description of your match then either wait a few days and check back or pay to have yours appraised by one of several guitar specialty shops (Gruhn's Guitars in Nashville comes to mind.)