I've been trying to find one of these for years. Finally acquired this in a trade. Only know of 2 out there. Let me know if you know of more.
The bracket has a dog bone shape to it, and is embossed in the middle. The 2 spools it holds very much resemble the shape of the largest NET spools I've documented, but slightly smaller size. The spools measure 1-3/4" x 1-3/4", and are not embossed. They have a 45 degree angle that transition from the sides to top and bottom. No embossing. https://www.insulators.info/pictures/?id=522503954