Riken was the successor to Campways (i.e., buyout) and production moved from Japan (Tokyo, actually) to Korea. Late 1980s to early 90s? Riken built and sold a ton of boats in variety of designs, from Pioneer to Aztec, including Miwok, Cheyenne, Shoshone, Nez Perce, Hualapai (that's what the boat on KSL is) and others I can't remember. Early on they were boats, i.e., what are now called bucket boats, later self-fillers (i.e., self-bailers). Regardless, both Campways and Riken had/have great reputation for the durability of their Hypalon. (riojedi's comment notwithstanding)
The Havasu, designed by Vladimir Kovalik (sp?) of Wilderness World, was a game-changer in the 17-18' class and lots of its features were incorporated by later big S/B rafts. There are Havasu's (I, II, and III's) still out there today, almost 40 years after production, running big water (Cat and the Grand, mostly).
NRS bought the Riken designs (Nez Perce and Hualapai at least) when Riken went OOB early 2000's. Production moved to Mexico, far as I know.
The Charger and River Rider and some Pioneer models are not quite as stout as the "commercial" quality boats manufactured by Riken. But I've seen all three boats in the last couple of years in Cat and on the Grand, properly cared for they last a long time.
I cut up my last Havasu rather than try to sell it for a "project boat." It would still go anywhere but was 2X or even 3X daily pumper and eventually the fabric rot just got beyond comfortable for extended trips. There are still a couple of Havasu III's at my pard's warehouse that are ready to run anything tomorrow, but you do need to pump 'em every morning - and maybe evening, too!