For the details of the markings on each of these and a look at the 14 New Arrivals and a duplicates list for trade or sale, check out the page: http://home.earthlink.net/~davfoun10/fenceknobs.html Here is my collection of porcelain electric fence insulators, nail-knobs, house insulators, spools and other similar looking insulators. The gray one on the very top-left came from a civil war era dig site. It is very crude and has a couple nasty chips. The brown one on the top is from England. The aqua glass one in the middle of the third row down is a lightning rod insulator. The other glass (bluish) is similar to and the right size for a CD 1080 spool but has a smooth flat base, instead of being plunged. The top also appears a little different. The little triple grooved black insulator on the "F" row is made from bakelite, composition or some kind of cheap plastic.