John, regarding the date when the WM ball herald was adopted, there's a photo of a WM mill gondola (WM 50701) in the 1940 CBCyc which was delivered with the ball herald in 3-37.
In the Aug. '49 Model Railroader, the review of a Utah Scale Models Col 65 foot mill gon said "The sides are sprayed authentic Western Maryland white and lettered in red. The lettering is perfect."
Is this true? (the color of the prototype that is) - John