Hi Sylvain, yes these days roller reefing is a bit of history, when I first started sailing Wayfarers 30 years ago roller reefing was sometimes seen. People would roll a sail bag into the sail to make a boom vang. But “jiffy” reefing (or slab reefing) is normal now and has been for sometime. Your boat number 3380 would certainly date from a time when roller reefing was done.
Anyway, just to clarify the mainsheet (“rope”) does go on the bottom of the swivel.
On the photo it looks like there is a hole at both ends of the swivel (top and bottom) – in which case a topping lift / balancine is optional. Most dinghies don’t have both but a few do.
The sail outhaul would go around the slots.