This is a close up of the a 10" Locke. The backwards N is cool, but my question is about the symbol next to the K. What is it? And... I have this symbol on the bottom of an old cork-type bottle, but the K is inside the symbol. I have seen old bottles made by Hemingray on eBay, so is this bottle possibly made by LOCKE? Thanks for any help. Elton Gish helped me on this one. He says: Locke had nothing to do with the manufacture of glass insulators and Hemingray had nothing to do with the manufacture of porcelain insulators. You should not assume one item has anything to do with the other simply because a similar odd symbol was used on both in a completely different way. The symbol you refer to is the "keystone" often symbolic of Pennsylvania because it was the "keystone state". It has no significant meaning for insulator collectors and could be just a notation for a particular order of suspension disks. The Locke 580 was a EEI-NEMA standard 52-4 style. ... Thank you!! This is why I like ICON. I can usually get the right info fast and I always learn something.