Don't see these too often. A nice green OVGco with a little amber swirls, they can be seen the best in a light box. Has a little roughness to the inner part of the base. Looks like an "insulator kiss" on the wire groove when insulator was still hot, touched another and made an indent. But could be a sliver chip, but to me it looks like a "insulator kiss". The kiss can be seen above the "Co" in the picture. A wire groove rub and rub below "Co", can be seen in photo. Over all I would rate the insulator VNM. Price guide 175-200, my price $ 170, now only $131 plus shipping.