Before starting disassembly it's a good idea to wrap a length of sticky tape around the front and two sides of the clock towards the bottom, from one rear pillar to the other, to prevent the front and side glasses falling out as you remove the case.

Turn the clock over and peal back the felt covering the base at each corner, to reveal the holes for the screws holding the four brass case pillars to the base.

With a suitable screwdriver, loosen all four screws just a little. They may initially be fairly tight. Do not let the screwdriver slip in the screw heads. Do not remove the screws just yet.