Here's a nice find on YouTube... from the description:
- Implementation and early development of a fully detached, gravity impulsed, mechanical escapement inspired by the designs of James Arnfield. Prototype built for kinematic amusement with the possibility of satisfactory timekeeping.
The pendulum should at no time be connected directly to the going train and only impulsed by a falling tumbler which, after leaving contact with the pendulum, releases the escapement.
If you know more about this, I'd love to hear from you. Looks fascinating.