Nice score. Yep, it's all Japanese stuff, except for the pups. Those are generic, latter day Chinese pups with brass baseplates, stamped 'N' and 'B' for the respective positions, and a typical ceramic single. Looks like it's wired up without the split hbs in positions 2 and 4 as well.
The 1992-93 RG450s were some the more basic spec Japanese models - they differed from the 550 in the lack of a tilt neck joint, as pointed out, and a plate mounted jack, as opposed to barrel. They still had the V1/2, S1 pups, Edge trem, and mostly rw boards.
The Wiki and catalogues don't always give the full picture of all the models what were out there. The only 460 of the time I'm aware of was a HSS, 22 fret model with the TRS 101 trem. It's possible that there was a 24 fret, Japanese, maple version was for a particular market or spot run.