I visited the British Museum a few weeks ago while in London for a conference. Amongst their collection was this interesting item: a fully functioning crown and verge movement.
In the secong photo you can see the "foliot" bar with the two weights and attached to a circular ring.
Originally there was no ring and the movement of the bar with the weights could be quite erratic. Hence the name foliot from the French "fol" (mad).
However the movement of this "balance spring" was still not entirely stable and was affected significantly by gravitiy. It was only with the use of a pig's bristle acting as a sping that made a major improvement in function.
The crown or escape wheel is seen in most of the photos and the upper verge in some. The lower verge is seen with difficulty in the first photo.
The drive is a fuse type.
I believe this an original movement and not a copy.
The machining is quite crude.
The other interesting feature which you will see by their absence are hands (look Ma, no hands!)
These movements did not have any. They struck the approximate time to mark some religious daily event.
It was only later that the hour hand was added and much later with an improvement of the movement's precision that a minute hand was added (with the appropriate gearing , of course).
If you are in London, their watch and clock section is definitly woth a visit.