Here is a picture of my cobalt diamond. I had a hard time getting the color even close, but was able to get a reasonable match (on my monitor) in photoshop. It is somewhat darker and leans closer to true "cobalt" in life than the picture, but does not match a Hemingray cobalt. It has a small 7 on the back near the base. There is a flaw at the base to the left of the diamond in the picture where a small piece of broken glass got stuck in the soft insulator in the mold. There is a depression and a tiny remnant of the piece of glass still in place. There is a small amber streak down the front, which is more visible in the picture than in the actual insulator. I found this in about 1975 in southern Quebec on a pole for a telephone drop to a small building.