Published by Professor Puzzle, this is part of the “Letterbox Lovelies” series, which you buy and post to the lucky recipient. Curiously, I can't find it online.

It contains a pack of 50 sheets of “same both sides” paper and a very thin  14cm booklet with 14 designs condensed within. Some of the diagrams were by me, others appeared as if by magic. All models were renamed and my name doesn’t appear anywhere…