We have always considered and collected these commercial masks and helmets as industries tribal art. Examples can be elegant in their simplicity or bazaar and complex. They are always unique, suprising and filled with personality.
1914 DUCK Model 5BB Navy Type Receiving Transformer
This was manufactured and signed "Duck". Its one of the more elaborate configurations. It looks very clean.
Also known as a "Receiving Transformer", loose couplers were used extensively in receivers built during the "teens". The coupler consists of two coils, a primary and a secondary. The primary coil is stationary and is usually provided with a slider for varying the inductance by single turns. The secondary coil slides in and out of the primary to vary the coupling, and is designed with several switch points in order to change its inductance.
Loose couplers were used as the primary tuning device in early receivers. The primary coil was attached to an antenna and ground (sometimes through a variable condenser.) The secondary was connected to a detector (typically a crystal detector in the early sets... $1300