Designed to  be fixed to a breadboard used in the layout stage of a new experimental circuit  following the pictorial wireing in the latest issue of the 'Listener In'. These point to drawings in  the magazine article showed the shape and position of every heavy square copper busbar wite together wire its terminal. This open plan method came ahead of the symbols we now use to position every component part in a circuit. Using a pictorial layout plan was  a true indication of the years from 1920 to 1930 when radio  was sweeping everything asside as the newest and greatest hoby to hit the buying public. This picture showes the clamp screwed connection terminals on the top of the speaker, this method applyed to every  connection including the valve sockets and every other component almost without exception.  See the picture of the two tuner radio for a well detailed  inside view of 1920s  radio layout and construction.