As a model railroader it would be tempting to do that car anyway...but normally realism and plausibility come from modeling the mundane rather than the exceptional. To that end I see several Grandt Line former C&S cars with plain RGS lettering in my future instead of this much more exciting (and incorrect) scheme.
I guess the other tip-off would have been the lack of dimensional data. I know by the 40s quite a few D&RGW 3000-series boxcars were rolling around with only their road number re-stenciled but it would have been silly for the RGS to have taken the time to add the sunrise herald and not replaced the dim data.
Oh well...thanks for setting me straight!