It’s based on Ralph Laughton’s Nano Roundabout from a few years ago but using the 6” Pulley at the top. I’m calling it a Mini Carousel (mini roundabout sounds daft!). I’ve built some rather crude horses instead of Ralph’s nano models.
I think the 6” Pulley came with the 1970s № 10 set, but I’ve never used it until now! There was only one in the set and, as far as I can tell, it only appeared in one model: 10.15 the Showman’s Traction Engine which I’ve never built.