A pack of three reels, each containing 7 images - actually 14 pictures on each reel, taken with a special camera which mimicked the stereoscopic way we look at the world.

Here's the science bit. Each of our eyes sees the world from a slightly different position, so when each eye sees the same picture (but taken from slightly different angles), our brain perceives it as depth. Hence the 3D effect with View-Master.

A photographer armed with one of these special cameras visited the Century 21 studios in Slough during production of the episode Attack Of The Tiger, and took photographs of the puppets and models "in situ".