NNG identify this SG Caboose in Colorado

Can any SG caboose experts tell what age and road name of the caboose in the attached photo? It is located on a open meadow not far from UP Cheyenne to Denver line about 12 miles East of Longmont, CO. UP, C&S, or Rock Island? Was outside bracing common in caboose construction at some point or was that added by the railroad later to keep the thing from falling apart? Note it still has trucks and couplers, and is on a very short piece of track. Can't read the casting letters/numbers on the bolster. Photo taken from road as no trespassing sign was honored.

Craig Miller
Longmont CO