The description says this was the Ibex Branch which ran east out of Leadville to serve some very high altitude mines. The Ibex Branch was not part of the Tennessee Pass Route. I believe the Ibex Branch was converted to standard gauge in the early 1920’s, about the time the third rail was removed between Salida and Leadville. It was abandoned around 1944. So this photo could have been taken any time during the narrow gauge years, though engine details might date it.
If Jerry Day sees this, maybe he can add to or correct what I have said. He is quite a student of the Ibex Branch.
Bill M.