Originally Posted by silversmith
It's a Sakae Ringyo. They're best known for their cranks, stems, and seatposts.
I don't know about their Gran Course, but I've got one of their beautifully made lugged aluminum bikes that is both lighter and stiffer than a similarly constructed Vitus.
I could easily be mistaken, but my recollection is different - that SR bikes were imported from Japan by a company that was completely unconnected with Sakae-Ringyo, the component maker. There has been some discussion of them on the forums at OldRoads.com over the years. It might be worthwhile for the OP to spend some time using the search function there.
My faint recollection from the era - 80's thru early 90's - is they mostly went to Canada. This started in the years just before Canada slapped prohibitive tariffs on imported bikes. It was rumored that they were coming from the same place as Miyatas and Nishikis, or from Sekine (which eventually opened a plant and made bikes in Canada), and that the "SR" name was an effort to sound less Japanese (I guess "Bridgestone" was already taken.
). By all accounts, in any event, they tended to be very good frames, mostly brazed from Tange #1 and #2, but they also had an excellent aluminum frame in the early 90's.