These hard to find ads are from Mogadore Insulator Co., One showing strains they made. Trenton Porcelain Co advertising their Jiffy knobs, Cook Pottery Co showing their Wedge split knobs, Starr Porcelain Co. advertising their oval shaped split knob. I have one complete knob and some bases without tops and they are neat. Last is a General Porcelain Co. ad showing some of their products and the company grounds.