2 Dollars - Elizabeth II Chromadepth

Niue's licensing arrangement with the New Zealand government allows it to issue legal tender coinage despite having no central bank and a population that has never meaningfully circulated its own coins. The "Chromadepth" series exploited a specific optical printing technology developed by American Paper Optics — a lenticular-style ink process that creates the illusion of three-dimensional depth when viewed through proprietary red-cyan glasses originally designed for NASA imaging work. The coins were produced by the New Zealand Mint on contract.

Collector fodder, essentially. But the print technology itself is the point of the object.