Zebco 33

Junior set his brand new Zebco 33 down at the waters edge where the waves promptly lapped so much sand inside it that it was completely frozen.  I've stripped and cleaned the front assembly down to the spindle, but for the life of me I can't figure out how to get the rear cover off.  I see the little dedents on the bottom, but the seam is pretty tight and doesn't yield much to a screwdriver and I'm afraid putting more force in will deform it permanently.  

What is the correct way to remove the rear cover?