Boxcab, I've contacted the AAR and would be surprised if someone replied in the affirmative. Thanks again for your help.
OK. I have finally had a few spare minutes. A newly built page on my web site displays a complete Milwaukee Road Standard Signs book. It can be seen here: https://train-orders.com/MILW/SSB/SSB.html
That is exceptionally cool stuff Boxcab. Thanks a bunch for the link! Amazing that states like Minnesota regulations governing exactly how highway crossing signs had to appear. The Milwaukee dutifully complied with a page to address it.
There were many variables, and I would get a headache trying to recall a lot of them. One in particular, although not signs, were cabooses. Washington had a law, and the MILW had to assign cabooses otherwise pooled, which were self-contained.
