Steve,
Neat photo! Judging from the fresh paint, extra flags and time of year, I would speculate that it may be a shot of #74 on a test/break in run in the early part of 1949. The RGS bought #74 in the fall of 1948 and gave it a once over in the Ridgway shops during the winter of 1948-49. This is also the only shot of #74 on the RGS that I have seen where the locomotive does not have the screen cap on its stack.
Jason Midyette