When did RGS coaches get windows boarded up?

Thanks for all the information posted so far! I was especially interested to hear just how the RGS executed its passenger service in the last years before the Geese.

My understanding based on what's been said is that by the late 30s, these cars were (almost?) all painted into a freight car red with white letters for MOW service.

So, when I see coach 260 in Rico in 1939 still looking like a coach (no windows boarded over) I'm assuming it's red with white lettering in MOW (B&B in RGS speak) service:

RGS_260_at_Rico_1939

And then years later in the late 40s and 50s we see it with some of the windows boarded up, now very clearly red with white lettering and with the road number changed to 0260:

RGS_0260_at_Ridgway_1953

...which is a very interesting subject to model in its own right. So the next natural question is, when were some of the windows boarded on the 0256 and the 0260?