THERE IS A GAP AT THE BOTTOM RIGHT OF THE CLOCK THAT YOU CAN SLIDE A SCREWDRIVER IN WHICH SHOULD RELEASE THE CATCH AND THE CLOCK PULLS FORWARD AND UP. MAKE SURE YOU ISOLATE THE POWER SUPPLY FIRST TO SAVE YOURSELF FROM DAMAGE, YOU CAN GET A STRAIGHT REPLACEMENT THAT JUST CLIPS BACK OVER THE OLD BACKPLATE.
ANDY, October 2007