This rare M-3068 Canadian Porcelain 3 part insulator was used on the upgraded 25k transmission line to Copper Cliff Ontario. The CP shown has no damage despite years on the cold ground. The shells are very close together with not much room to expand in the cement joint. Many would crack from frost. I just got back from another trip to the outback of Canada to look for this type. I was able to recover a center cemented to a bottom skirt on an original pin as well as another nice whole bottom skirt with a blood red glaze drip.