Epson Progression U12 - Manual (Page 61)

4.
Loosen the three thumbscrews on the computer’s back panel
by turning them counterclockwise, as shown below. (The
screws disengage but don’t come all the way off.)
5. Grasp the sides of the cover (toward the front of the
computer) and pull it firmly toward you, as shown below.
Then lift it up and off the computer.
2-4 Accessing Internal Components