It’s a Nitto uplift, though I don’t know the number. Uses the same seat post clamp as the R10.
I used it with a Carradice Barley bag on the GAP and C&O trails, Pittsburgh to DC. Got mine at one of the Riv yard sales a dozen years ago. Interestingly, it had the same HB tape wrappings to keep the bag straps centered.
Recommend that you Loctite the single M8 bolt — There is a lot of stress on it! Mine loosened up with all the jouncing and stripped the threads. Once back home I got an M10 bolt and tap and retapped the aluminum clamp.
Also recommend that you run a strap from the saddle rails to the top of the hoop as extra insurance.
Best,
David Lipsky
Berkeley, CA