Looking for the same kind of informations to set an era for my Hon3 RGS First District futur layout, I went through this among other things:

RGS Engines

Helped to narrow down my selected era to Fall 1941 for almost everything, but I will go for some artistic license to add 455 post wreck and 461 with Sunrise herald to the RGS’ stable (really love those two). I imagined my RGS is still in Miller’s hands, a bit more healthier than the prototype because of better traffic (oil traffic back onto RGS tracks for example), and able to maintain it’s own engines, even if because of the traffic still needs to lease some D&RGW motive power.

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Sebastien
SNCF passenger trains engineer
Volunteer on the "Chemin de Fer de Rillé" (60cm/2ft, France)
www.aecfm.fr
cfrtrain.blogspot.fr