The darker spots that you see or "lines" are simply shadows as I perched this pair on the white hood of my car this afternoon. My friend Joe got the peacock one (on the right) back about 1987 from Jack Riesselman (he still buys insulators from him on eBay!). Anyway, the darker one (on the left) was in a long-time collection and we were recently fortunate to get the owner (a retired lineman) to part with it (gracefully). The municipal utility he worked for had some "blue" glass as markers for their street series lighting circuits. This fellow was saving out-of-the-ordinary blue glass insulators (according to Joe M) from way, way back. This pioneer collector (sorry, no name can be mentioned!) always was quite recluse about insulators as it was his private hobby. During the 1960s it is known that he did trade with a few other collectors and as a result added this darker CD 162 HG to his collection! Joe ascertained that most of these swaps were from phone company and electric utility guys in Illinois, Indiana, SD, Nebraska, Montana and Missouri.