Thank you!
After some research I agree it’s absolutely a placard.
I searched the all-time history on this site for more info and photos of placards.
I was hoping to learn more about where, and what they were used for, but only found examples relating to tank cars.
Does anyone have more info, or know of photos of large placards in use on boxcars?
Were they used for explosives only, or other types of freight too?
Thanks,
Ryan