| ▲ | 29athrowaway 7 days ago | |
You may also be interested in: https://en.wikipedia.org/wiki/EURion_constellation | ||
| ▲ | tgsovlerkhgsel 7 days ago | parent [-] | |
And the lesser known, newer, invisible, digital watermark based version of it. Unfortunately very little information is available about that one. http://www.cl.cam.ac.uk/users/sjm217/projects/currency/ | ||