Proper grade crossing signals circa 1948

[nw-modeling-list at nwhs.org]

What would appropriate grade crossing signals on the N&W in 1948 be, in 
urban and rural settings? Were they all still the stand-alone wig-wag 
signals, or were there other styles of crossing signals in place in 1948?
I'm not a rivet counter or a nit-picker but I want to be in the ballpark on 
my layout if I can be.

Bob Welsh