This B-1 photo is the Caribou Creek. Must have been renumbered at one time. When the steel (2nd) B-1 was acquired the wood (first) B-1 was renumbered to B-10.  Note the  enclosed rear, later rebuilt to an open platform.  It was named the "Caribou Creek" in honor of a US Army military exercise that occurred along the ARR (shooting from memory: mid to late 1960's) It lost it's B-1 at that time.