I recently discovered that Riefler (of uber-precision clock fame) also designed, and perhaps patented, a watch escapement that delivers impulse by the same principle as his clocks. The escapement displaces the outer point of attachement of the balance spring and so impulses the balance by cyclically disturbing the rest position of the spring.
Does anyone (TCP, John...) know if any examples of this were ever built?
I know there were a couple of other attempts at this way of impulsing (Lambert...) but I'm intrigued to know that Riefler tried it, given the success of his top-end clocks.
nick