The Verge Escapement is one of the earliest escapement mechanisms ever invented. Instead of a hanging side-to-side pendulum, it uses an oscillating inertial weight. The pendulum period can be adjusted by increasing the inertia of the pendulum. This is achieved by adding mass to to the ends of the pendulum arms.
Here is the video that shows how easily this mechanism can be assembled!
The STL File:
Prints on all standard 3d printers without supports, requires the following additional parts to assemble: