The idea behind this project is a lovely one: a small object built purely to puzzle friends. The maker set out to model a trick coin, and the whole thing was drawn up manually in Fusion rather than pulled from a library, which gives a nice sense of a shape being worked out by hand.
The token itself is octagonal, with an embossed arrow sitting in the center of the face. Around the edge runs a decorative border holding eight small circular indentations, and the surface carries a painted finish in a bronze or wood effect. As an object to hand across a table, that combination of geometry and weathered colour sounds very appealing.
The clever part is the mechanism hidden in the design. A pair of arrows sits locked at right angles to one another, and the whole trick needs nothing more than a single 45-degree turn plus a flip. The routine runs like this: hold the coin so the front arrow points UP, flip it over and the back arrow reads LEFT, turn the front 45 degrees counter-clockwise, then flip once more. At that point both arrows line up in the very same direction.
The trade-off is the human side of it. Tracking several 3D rotations at once is something our brains handle badly, and studies suggest most people lose the back arrow after the very first flip. The maker notes that only 9% of people manage to predict where the arrow will end up, so the odds are firmly stacked in the coin's favour. It seems like a perfect pocket-sized bit of mischief.