OK. I can buy a anti-counterfeiting technology handwave, even if it's a little hard to believe in a setting incredibly more diverse than the European Union is (where a monetary union combined with federalism and diversity of economies have led to substantial financial difficulties, albeit different than I presented).
It is a little hard to believe partly because of the inevitable, hard-to-track-down criminals who would presumably have the capacity to kidnap an engineer or three and start taking verifiers apart, in order to reverse-engineer what an undetectable forgery is supposed to look like. Replacing compromised countermeasures sounds like a nightmare, because presumably all legit Crimps everywhere need to verify as legit - unless you have multiple valid standards... in which case security is poorer, but you could limit damage; but it would still be horrifically painful to reimplement verification measures. I'm not sure issuing a new currency would go a smoothly as our RL currency changes do, simply because of the vast amounts of time needed to get information across.