Here is an old style 15,000 volt line break switch, one of 3 that I just acquired. To see the pole that they came off of [id=254540755]. The tag says that they were made by the Schwager-Wood Corp. of Portland, OR., a town I lived in for many years and I had never heard of them! The metal top multipart insulators on them are NGK Japan dated 1968 and look similar to an M-2751 with a longer pin skirt. My guess is that TPUD, the utility using them, replaced some smaller original insulators on the switches with these NGK jobs so they could be used on their 25,000 volt line. They are a bit heavy and my back let me know that after I had to pull them out of the dumpster bin!