SSMTBs

I think it's just a splitter for a poss belt drive setup !?

Though why would you have an adjustable chainstay without any pivot on the seatstay.

Simply because it’s not needed.

There’s a lot of spring in a steel frame. I’m not sure what the long term implications of utilising that spring in order to tension a chain would be (whether you’d be stressing the seat cluster joints or not) but as a serial chopper up of frames, I’ve never chopped a frame that didn’t immediately jump out of alignment by more than enough to tension a chain. I reckon that so long as you weren’t changing the setting every week it’d be fine.

Its a good insight into what you can get away with. Its too light for me - but interesting to know how the hitters do it!