Quite a unique and a very practical one for a bookmark - magnifying sheet and a bookmark in one. This is a very helpful tool for me, especially when i get older. *laughs* At least i don't have to buy me a magnifying glass anymore. A friend got this from a trade show in China, which she then gave me when she arrived home.
A sheet magnifier consists of many very narrow concentric ring-shaped lenses, such that the combination acts as a single lens but is much thinner. This arrangement is known as a Fresnel lens.