This is the Spiratone Circo-MirroTach Right-Angle Lens Attachment

The Spiratone Circo-MirroTach from the front

The Spiratone Circo-MirroTach from the back

Here is the original 1984 advertisement for the Spiratone Circo-MirroTach

This is a Spiratone Circo-MirroTach right-angle lens attachment. Touted in the ad as... "One of the most usefull accessories ever available for candid photography". This mounts to the front of your camera lens via the filter threads. Use an adapter for Series VII to your filter size. Once attached, it can be rotated 360°. There is a right angle mirror that lets you take candid photos, while it looks like your camera is pointed somewhere else. The ad explains it all with a diagram. A little creepy. The images will be reversed due to the mirror.