I was astounded when I saw this... We have had the "Muncie Type" Hemingray insulator in the CD 303 and optional CD 310 sleeve, and the CD 302. Now we have the "Covington Type" !!
A friend had bought a 1911 Hemingray catalog on eBay. Before that, no one in the hobby knew there was a catalog with that date... I asked to borrow it from him, and I was flipping through it, and I saw this piece! Yes, a CD 317.7 !! This is the first time this piece has ever appeared in a catalog. Only one known specimen exists. What an exciting find!
The actual specimen is embossed H.G.CO. with the MAY 2 1893 patent date. The only known H.G.CO. power insulator. This drawing shows it with a patent date of June 10, 1902. That is the date of the two patents issued to Vernon G. Converse for his multi-sectional insulator which we know as CD 317.8 / 313.1 / 313.1 / 313 or "Section 1".
Patent information is at