This style of wire holder is know as the IN-56 Signal insulator. It was a simple design used in WW2 and beyond by the Army Signal Corps. Everybody has probably seen or has one of the Hemingray made glass versions. It is the only glass version known. There are also several porcelain versions. They are all the same shape as Hemingray's but is rumoured to be made from different manufacturers. I believe that because they would have needed thousands during the war effort. The ones I have collected are all different. Here is my take/guess on the manufacturers. From left to right First one has lag cut off, No Name, possibly Hartford Faience Co., Second is the Hemingray glass one, Third is a chocolate brown one, I think could be Hartford, Porcelain Products or Knox?, Middle piece, nice mottled browns, rusty brown piece after that Locke?, Next piece Hartford Faience? with lag, Last piece mottled rusty brown with lag cut off another Locke? Would like to hear anyones thoughts on these or any info they may have.