In the Historical Society of Idaho Springs, book "A History of Clear Creek County" 2004 pg98, can be found a view (dated 1890) of similar perspective to Robert Grandt's Title picture at the top of this thread but with the addition of the long orebins facing the Siding as shown in this view.
http://digital.denverlibrary.org/cdm/fullbrowser/collection/p15330coll22/id/67645/rv/singleitem/rec/24 Like the Title photo showing the earlier building with a St Charles Coalcar, this purported 1890 photo shows a Coalcar, but with a Knuckle coupler visible.
I wonder if the "Locality" or the Siding was also known by the name "Smith Mill" as it was still called that in the 1922/1929 C&S trackage map of Idaho Springs shown on pg213 CRRA#10. The siding was still present at the "Last Train" photo by John Maxwell also on pg198 (middle) of N.G.to Central & Silver.