This is a very nice 1951 Buffet Clarinet received and sold as is. Apparently this serial number falls right in at the vague beginnings of the R13.  I do not know if this is one though.
Beautiful old case as well. I don’t see any cracks etc but not being a great clarinet expert, I mainly see lovely old craftsmanship. Buffet mouthpiece included as well!  This has been sitting a long time, will likely need some attention, but by the looks of it, also well worth it.