Found this one at DJIC, a wonderfully crude and funky little straw glass insulator, which looks every bit to be of Russian origin. No embossing, or other identifying markings. The inner skirt is somewhat deformed, and there are some milky streaks in the glass. I'm guessing that this one falls within the CD 505-506 range, just a SWAG... Base diameter 2 3/8 inches, and height 2 3/4 inches. (roughly 60 mm and 70 mm, respectively). The pinhole has only a couple of very shallow threads near the top.