This is the blueprint for a "thin base" Girl in Drum illusion. The illusion was invented by Chefalo around 1909, but copied and popularized by Tahyer in 1924, when they first sold the illusion plans. This model, by Paul Osborne, does away with the mirror base to use a smaller and less obvious thin base, although it is very basic. I think Mr. Osborne later released an improved version with a better design. The set is in an envelope, being 2 pages of instructions and the blueprint.