There is a fifth screw in the center, under the foil label. Lift the corner to find the screw and preserve the model number and barcode on the label. While you have it open, if you care to remove a few more screws, you can grease the gears to extend the life of the machine. There is one gear (the thin, large-diameter one in the middle), that strips out and stops the machine, but the factory grease is inadequate, so generously lube all the gears with a Q-tip and the best quality grease you can find.
Jerry, November 2013