What is "mimeoscope"

In 1914-16, the A.B. Dick Company patented the mimeoscope. A mimeoscope, which is basically a light table, had an electrically illuminated glass top on which the operator traced drawings onto mimeograph stencils. The stencil took the place of tracing paper. The electric light was needed because the stencils were heavier and less transparent than tracing paper.