During this process we will use symmetry and meshsmooth modifiers to see the mesh result

Before we start with the interior, we will link the three green objects with a helper to control their position

For the interior part we will do the same

The numbers are a text spline with an extrude modifier, and then an array over the clock's surface

The inner gears have been made with splines and a bevel modifier

To make the chain, we will prepare its parts individually

Use spline IK Solver to link the hoops of the chain, and obtain a custom chain the path