Vintage cobalt blue porcelain pony electric pole insulator. Marked "D" within a square. I believe they are a pin type insulator manufactured in the late 20's or early 30's by the Square D Co. in the USA. I believe this is style U-32.

Recess-embossed on the top; "D" inside a square which is the Square-D Company logo. Cobalt blue porcelain dry process insulator, bottom rest, glazed pinhole, pony style with one groove.

In excellent condition. Highly collectible. Makes a unique paperweight or decor.