Looks like it's screwed to the plate, I'll take a better look tomorrowIf that's home made, someone did a lot of machine work. It would seem easier to me to just knock off an 1100 Honda back rest to fit the 1300. But I've never really looked at the 1300 luggage rack.
Is the backrest flat plate welded or screwed to the round support piece? It looks like a flat was machined on the round stock and screwed to the flat plate.