Optical pufs

The first example of a PUF apparently comes from the cold war, when it was necessary to identify nuclear heads. The solution back then was to coat a layer of nanoparticles that would give a unique speckle pattern. If you record this pattern under different illumination angles, you can be pretty sure there will be no way of replicating the underlying structure (Optical PUFs).

When you are counting nuclear weapons, you want to be sue you are not double-counting.

You can have a database of speckle patterns and compare the output you are measuring to it. In this way, you can authenticate the object you are looking at. Moreover, without access to the original device, it is impossible to compute the outcome nor to record all possible patterns generated at every possible illumination angle in a reasonable timeframe.