New Zealand-based Weirdsky Industries offers these unusual three-legged calipers which express the golden ratio (Wikipedia), dividing the distance they span into two sections such that

The golden ratio is ubiquitous in the natural world, and in art and architecture at least since ancient Greece.

The calipers are made from laser-cut stainless steel, hand-assembled using brass rivets, and are produced in three standard sizes, with custom sizes available on request.