During some mending of some old jeans using my 1957 Singer 306K sewing machine, I encountered a jam of some sort and was forced to go digging to find the cause. I eventually found the offender (some balled up thread in the bobbin) but during the careful diagnosing and dismantling of the moving bits inside I found something interesting.
Now, if you needed a timed coupling between two shafts and Mr Gilmer hadn't invented his rubber toothed belts, how could you make a non slip connection between two pulleys? Here's Singer's solution.
How about a belt made of 11 wraps of heavy twine with carefully spaced bent steel wires clipped around it? (Simanco Part No. 189651). Singer was one of the first users of the rubber toothed belts developed in the early forties by Gilmer, but this old school belt is going fine after more than 60 years.