Rail car porcelain sign" dont spit in the wagen" help identify please

[hertzyinmn]

hi, i have this very old porcelain on steel signe thats 3 1/4" x 6 3/4" and is very well made. it mentions For health sake we strongly suggest do not spit in the wagen,, it is marked GLADIATOR on reverse and I really would like to know where this came from, i have been told on collector weekly that possibly was a bmw or volkswagen item as the military was forcing labor there , well any help appreciate , thanks