Here's a couple more old industrial warning signs that came to me from a now demolished Pabst Beer brewery in Peoria, IL in the early 1980's. I now have these two displayed in my kitchen over the stove, a location that just seems appropriate to me somehow...? <lol>
Both are made of sheet steel with their legends painted on. The 'face shield' one measures 14" x 20" and features what is apparently the result of a "drip/splash" of the dangerous chemicals it warned about, near its RH side there are a series of small spots on its surface (appearing gray in color) where the paint has been completely eaten away to the bare metal underneath, though without any rust/corrosion. (?!) The yellow 'caustic' sign is 12"square and actually two sided with "WET FLOOR" on its reverse -- it was originally part of a pair attached to a stiff wire stand that made up a 'portable' sign as used by janitorial personnel.