Russ,
According to the photographic evidence, the 9 hauled the last passenger train from Denver to Leadville and return in 1937. The changes made for the 1939 Chicago Railroad Fair were minor. There was a CB&Q style number plate made for her and she was lettered as the broad gauge C&S locomotives were with the square "Burlington Route" trademark on the tender, smaller cab lettering and the "C&S" below the cab locomotive number.
I'm not sure if the 9 made any trips up the Clear Creek Lines after 1937, although if it was needed, it would not surprise me in the least.
The biggest changes were made for the 1949 Railroad Fair, when the 9 got a fake diamond stack, a wooden CB&Q style horizontal wooden pilot and got painted red and named "Chief Crazy Horse" as a not too convincing stand in for the Deadwood Central, for which it was lettered.
The C&S passenger equipment also got a paint job as well, going from the standard coach green to a bright yellow, also with "Deadwood Central" lettering. BY 1949 the C&S 3' gauge was a distant memory and is unlikely that any of the C&S management had any say in what was done with their locomotive.
This lack of control was evidence when Ralph Budd (President of the Q) "lent" the C&S train and equipment to Elliot Donnelly for use on the Black Hills Central Railroad in Hill City. Donnelly, a Chicago Publisher, was a major stockholder and one of the moving forces behind the Black Hills Central. I have seen photos (postcards) of the 9 with smoke coming out of her stack while at Hill City and her use up there was intimated by the captions on the postcard. Not being up there I can't really state for certain that the 9 was actually used in regular Hill City service or not.
I do know that the owner/operator Bill Heckman, (Post Donnelly) felt that the 9 was part of the Black Hills Central Property (even though he could produce no proof of ownership whatsoever) used the 9 as a spare parts locomotive for which parts he could swap with whatever locomotive he had running. When the CHS was given the 9 it was on Heckman's orders that the parts like the boiler checks, the bell stand (with the hole through it for the throttle), and the injectors be torched off the locomotive to create the maximum amount of damage possible.
Just a bit of background...
Rick