Thought I,d post some of the unusual radio insulators that I and my father have. This picture is of transposition blocks and related. Left to right: No Name (Isolantite) transposition block, Johnson transposition block Pat No. 2,043,754, No Name square crossover and transposition block, No Name triangle crossover and transposition block. These were both advertised and manufactured by Porcelain Products Inc. and Knox Porcelain Corp., last is marked ICA/USA/NY/ /302/star in a circle(Star porcelain Co) Cage type line spreader transposition.