Those are interesting. When I was very young I purchased a Lucas Cyclometer, pretty cool until I rode beyond 14 mph.
in the fine print of the instructions as a warning to keep 14 mph as the max.
if faster the force striking the star wheel knocked it out of phase and destruction and or deformation would occur.

Even on a Sting-Ray 14 mph was typical.
downhill?

i removed it within a week.

those do look cool though. Lucas had different models for various wheel diameters, one might wonder what these were calibrated to.

later the Huret Multido with the O ring belt drive seemed better.

years later the IKU tire drive speedo/ distance tracker was the rage among some clubs. Its problem was going too fast would cause skipping, the drive wheel was plastic.