There are two silver, 6 mm-long machine screws with two 1/8" inner-diameter washers on the exterior of the metal electronics box; remove these first using a #2 philips screwdriver.

There are five of the same type of machine screw (silver, 6 mm-long) remaining around the metal electronics box's exterior; remove these as well.

You should have removed a total of 7 machine screws and 2 washers.

The reason for removing the two screws with the two washers first (or replacing them last when reassembling) is that their holes are actually slots. They are designed as slots to accommodate slop in the assembly, and if unscrewed out of order, you may have difficulty while removing - or possibly even damage - the other five screws.