There are two small tangs, one on either side of the CN-50F ports, at the top of the vent slits at the rear of the case. With your trusty case-cracker in the seam and applying a little opening force, gentle inward pressure on those tangs will lift the lid enough to clear them. There are then four horizontal slots, two on each side, where again you need a gentle parting of the seam at the same time as you push through the slots with enough pressure on the tangs attached to the lid to clear the retaining rectangular 'fence' around each one. When you have the case apart it will become clear what the retaining mechanisms are. I have taken the tops off each of those 'fences', which are a right royal pain in the fundament, leaving the verticals as guides during reassembly, on all five of my SC cases.

de