plastic haz-mat semi trailer placards

These three double sided signs are from a set typical of those used by professional truck drivers when hauling loads of "dangerous" materials -- similar are often spotted mounted in little metal frames and displayed on the sides and rear of trailers, as a (mandated) warning to those that'd be involved should something unfortunate happen to the shipment while in transit. They're 11" square, made of sturdy flexible plastic.

Their legends denote an assortment of hazards, color schemes and symbols are 'standardized'. (I don't have any idea what the blk/wht 9 means, though?) They got moved and ultimately rearranged today (to make room for the BEEF sign showed yesterday) so pic 1 is one side of each, pic 2 is the other side of each as turned directly around, and pic 3 is today's choice of which sides to leave in view.

I got them from a junk store somewhere along the line, and they've been on my kitchen walls ever since joining a few other key 'signs' that have always struck me as particularly appropriate for *my* kitchen...?? ;-) ;-) Pic 4 shows the BEEF sign in its new place continuing around the clock with a couple more of those 'wall accents'...I really need to swap in a more interesting clock, now... <lol>