Correct me if I'm wrong(which is a lot), but the Tyco "Royal Blue" was a generic paint scheme applied to that loco.
Like mentioned above, the real B&O "Royal Blue" was a premier passenger train that ran from Washington DC.. Hence the presidental names on the passenger cars.
From what I remember reading, the real "Royal Blue", was headed by a 4-8-4 "Berkshire" type loco. In the late 50's, these were replced by F diesel units(May have been E's). Just before the mid sixties, with falling revenue, the "Royal Blue" was discontinued.
So, though you have a nice collectors piece, there is no prototype match.
If you are just looking for an era to base your layout on, using that loco as a starting point, I would go with the late 1800's to early 1920's or late 30's.