The HD-R started production in 1986 and replaced the HD-S. In Japan there seems to be a whole class of "construction/ work record" cameras. Tough straightforward and weather proof. Though common in Japan they are less common in the US market.
HD stood for - Heavy Duty. Not sure what the R and S stood for. There was also an HD-M, motor driven version and an HD-P, panorama. The R seems to be the sweet spot it added DX capability (to 400 ISO) the S and has the focus on the top with an easy to use knob. On the S the focus was on the lens but still a zone focus. The M added a motor but I saw some talk about it being less reliable. The P masks the top and bottom of the frame to give a “panaramic” effect, but can also be shot in regular format. The P is also a manual film advance so it could be a good alternative to the R.
I really liked the HD-R as an adventure camera. It is simple to use, industrial strength, rated to 2 meters under water and produces nice images. It reminds me a mini Nikonos V. The viewfinder is not great, but this is more of a general direction kind of a camera. I took it on a kayak and was never worried about getting it wet of having it bounce around in the boat. I love that it has positive buoyancy so it floated when I dropped it. Plus it runs on 2 AAA batteries and has a big switch on top for the flash.
It is not the camera for all (or even most) jobs. Built like a mini-tank it is too big for a pocket camera. But if your going to the beach, snow, rain, or general abuse this is a great option.
Lens: Fujinon 38mm f2.8
Film: FujiColor 100
Manual for HD-M (motor drive was as close as I found) http://www.cameramanuals.org/fuji_pdf/fuji_hd-m.pdf