That reminds me of another 'wacky warning sign' story. I was stationed at Eglin AFB in Florida back in the early 90's. Eglin is a huge base with many square miles of woodland. Some of this is used for bombing ranges and EOD training, missle tests, Ranger training, etc etc. But most of it is open for hunting and camping etc and it is laced with miles of sandy roads of various levels of improvement.
Well, I was out there scouting one day, driving these roads waaaaay out in the middle of this massive property. I began driving smaller and smaller of these roads to the point where I was in 4 wheel drive and barely making it, totally lost. Finally I see a fence line up ahead with an open gate and a sign. I was relieved to be getting back to something like civilization and that the gate was open. I was disappointed to see that this large wooden sign had nothing written on it. I drove through the gate and looked back at the sign which said:
Danger! Do Not Enter. Unexploded Ordinance!
Needless to say, I kept going and did not look back again! I have no idea how I got into the area but I can say for sure I saw no other signs and drove through no gates that indicated I was somewhere I should not have been.
