A resin known as a paste is used as the material on the outside of the wiring accessory. In the initial phase, this was not a chemically manufactured synthetic resin but a natural resin from Southeast Asia called Copal. It was formulated together with clay, tar, carbon and asbestos. The actual pots, foot operated machinery, die pressing machine, and other machinery used at the time to make attachment plugs can be seen. Once can readily see that it started from formulation of the material using a mortar and pestle, and furnace. This paste technology formed the basis of subsequent development of plastic molding technology.