I saw a sign by the swimming pool shower "swimwear must always be worn". That was over a decade ago and it's getting ruddy itchy by now!
A sign in Sheffield used to advertise 'Stainless Steel Windows'. I can't think that they'd let much light in.
A carpet shop in Boston, Lincs had it's window display full of 3' wide carpet, 6' carpet, 9' wide carpet and 12' wide carpet, all priced per square yard. The name of the business, proudly displayed above that window, was 'The Metric Carpet Shop'.