[QUOTE=Has anyone else ever seen a "belt" like this, or is it a cob job???
[/QUOTE]
I haven't seen any in person, but here's a reference to the spring steel coil belts:
http://dragonpoodle.blogspot.com/201...c-treadle.html
(with reference to the McMaster Carr sales site)
This would be good for an interchangeable-head treadle stand, as the belt could work at a range of lengths.