The caboose would have been a charter on a Chama-Osier round trip. The box car is the concession car, the gon is...well...the gon. Both were always on the train. You cropped out the concession car and gon in your shot west of Antonito. At this time, the engines went through, the cars turned back at Osier, unless it was a charter caboose that was chartered all the way through, then it changed trains and kept going to the other end. The concession car and gon were kept on the end of the train away from the engine on the long/steepest grades, so they were on the east end of the Antonito train and on the west end of the Chama train.