I ran down to the local auction after work. There was a small basket of nicer but relatively common stuff pictured in the listing. As usual, I forgot to bring my price guide with me. When I looked at the basket before the auction started, I pulled out this weird spool thing. I've seen lots of porcelain spools that look like this, but never a glass one. Didn't know what it was until I got home and could look it up. Wow!

3/25/18 Since I just pointed to this picture from an ICON email, I will add what additional information I know about this piece. Hemingray experts have told me that is was an experimental mine insulator style that never went into production. All (I believe) other examples of this style have been dug from the Hemingray dump and are either partial or reconstructed pieces. This piece is the only completely intact example of this style, I believe. There is a rough area in the pinhole that might indicate that it saw service in a mine. My theory is that some samples of this insulators were sent to coal mines in Western Pennsylvania to see how they stood up to actual usage.