4, 2 and 5 look very grotesque, but the 1 is more
geometric sans. Bizarre…

I would say it is more probably handpainted.
Do you have a picture of the whole wagon?
Did you notice what the numbers on other trains look like?

If your looking for train fonts this is the spot:
www.railfonts.com.

I’ve looked through all of them, and I think the
closest to yours is the Egyptian lettering from
Southern Pacific. The 1 is the only character
that is radically different. Also notice the 4 is
very dark like your sample.

http://www.railfonts.com/cgi/font-store/fontshop.cgi?ACTION=thispage&thispage=page12.html&ORDER_ID=124557260

Randy