Some years ago, we took delivery of a small number of Pseudoscopes, designed and made by Terry Pope, who is probably the UK expert on devices of this kind. It was made to a very high quality, it was supplied in a metal flight case, and it cost USD750! After they sold out, we sold a cardboard construction kit to make a Pseudoscope, but it was time consuming to make, and the lack of glass front silvered mirrors reduced the quality of the image. It was very cheap though. Now, however, we think we have the best of both worlds. Designed by Terry Pope, this Pseudoscope kit is made from precision laser-cut pieces of acrylic plastic, and it is supplied with 4 glass mirrors. Although you do need to put the Pseudoscope together yourself, it is a much easier construction task than the cardboard kit, and delivers a high quality Pseudoscopic image. 

The Pseudoscope creates one of the most remarkable of all optical illusions, and was first described by Sir Charles Wheatstone in the 1830s. The Pseudoscope swaps the incoming images, so that the right eye sees what the left eye would have seen, and vice versa. The Pseudoscope therefore does to front and back what a mirror does to left and right. This means that foreground becomes background and visible background becomes foreground, or more simply, background advances, foreground recedes. 

When you view objects with this scope, the convex becomes concave. A tree turns inside out as it were - it's front branches appear at the back, whilst the back branches come out in front, hanging or suspended in mid-air as their support is eclipsed by branches in front.