Can't split Bosch PSB 18 LI-2 case?

I am trying to take apart a Bosch PSB 18 LI-2 and I have undone all the screws. I can separate the two halves up to a point - the bottom edge doesn't want to split. Has anyone encountered this problem, and how did you get around it. It's almost like there is another screw there but there is no trace of a screw anywhere.
Tom, October 2013


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