I have a small collection of banknotes, among which include occupation bills from various powers during WW2 and bills just before and after a major switch in governments (before/after Russian Empire/Soviet Union, before and after the Iranian revolution, etc.).

One thing that's always been interesting to me with the new bills is how quickly new governments (invaders or usurpers) put in place new, high quality, currency. It's almost like, along with the artillery and occupation force, engravers are the next to be flown in and put to work.

> "The issue for us is it needs to be a security document . . . [but] it’s also a cultural document,"

I find the cultural document the most fascinating thing about collecting money. Governments tend to put on bills the most important propaganda they can think of. Important buildings, people, public works projects, cultural activities and myths. I don't care much about the monetary value of what I collect, but the place in history that money represents.

This new currency is definitely going to be cool to add to the collection.

> engravers are the next to be flown in and put to work.

To elaborate on your point -- stabilizing the currency is pretty much job #2, and one that is worked on in parallel with job #1, by different groups of people. The bills are often printed back home in the occupying country, and the occupiers often have time to prepare.

We see businesses start up, shutdown, or get acquired all the time, the processes are familiar. Countries going through similar cycles are fascinating because we don't really know the playbook. But it exists. :)

A note is clearly a proof-of-work currency concept. As stated, it takes months of work on expensive hardware. Anyone with better/more equipment can beat them but it requires an investment in a field where they have a huge headstart.

Australia has had polymer banknotes for 25 years now. Canada just went polymer, using the same printing presses as Australia (the first Canadian 20s were actually printed in Australia until Canada could get their own printing presses)

As a world traveler, I'm always excited when I see countries that have gone to polymer notes - even poor ones - Guatemala years ago, Guinea now has a polymer note.

I'm still utterly shocked the US does not have polymer banknotes. Sometimes I think "because that's the way it's always been done" will be the end of moving forward in the US.

I'm european and recently got some new dollars because I was flying to Peru and had to spend a night in U.S.

I remember laughing out loud to U.S. funny-money. It's texture is closer to toilet paper than what I'd expect from the worlds most worshiped currency.

And all the bills look identical, have identical colors (although the latest series finally introduced some variation) and are the same size!

The "same size" has ADA implications for low-vision persons, so it's possible that'll change some time. It has some advantages, though, for places that handle cash to have it all the same size (cash drawers, wallets, vending machines, etc).

Once tipped a guy $11 for telling me an interesting story because I mistook the $10 as a second $1. Baffles me that the US hasn't upgraded.

I have a feeling the next generation of U.S. notes will probably end up as a polymer. A friend of mine worked for a while with the Bureau of Engraving and Printing about a decade ago and said that polymer notes were being tested, but at that time, none could survive the very rigorous durability testing the U.S. uses while the linen paper just barely managed to.

But we're in to second or third generation of polymer notes now and the chemistry has improved to the point where they'll make it through the ringer. However, like this article points out, banknote R&D has many years of work behind each issuance, the new U.S. notes that are just now coming out started development 10-15 years ago and the new ones use a new paper formulation. Bonus, the U.S. gets the benefit of observing the results of field usage for other nation's banknotes before committing to a couple trillion dollars in cash printing (more than any other nation).

Here's a brief video on the evolution of the U.S. Banknote https://www.youtube.com/watch?v=QjLD2B5I9yk

https://www.youtube.com/watch?v=2DaVsmsHq0E

Here's some videos on the type of durability testing from Canada's new bills

https://www.youtube.com/watch?v=8odUVIAXPS8

https://www.youtube.com/watch?v=-lDHLNgtzao

and an example of where they fail the test https://www.youtube.com/watch?v=znfOzuCBpAc

> I'm still utterly shocked the US does not have polymer banknotes.

US banknotes are tougher paper than other non-polymer banknote papers, and their longevity is remarkable. They're tough enough that it's still more economical to print new $1 bills then to switch exclusively to a dollar coin (even assuming everyone used the dollar coin.)

Few in the US seem to know this, but all ATMs in China have been recording currency serial numbers for several years now. It's an option on US ATMs and currency counting machines.

Makes sense. These days I just assume everything that can be recorded, is recorded. And kept forever.

What is the significance of this? Tracking who has what money?

Purchases you make with cash you got from an ATM become traceable to your bank account.

That only works if every single shop/service tracks the serial numbers, otherwise you have no way of knowing if they were exchanged somewhere in between.

You don't need to step very far from cash in hand before this becomes not just viable but ridiculously easy. Just feed notes individually into your bank-approved combined till/safe/note scanner.

I think you understimate the effort of requiring everyone - from large chains to street food stalls - to always use note scanners.

Bank? How many people selling fruit from their cart even use banks for their sales?

It's a very small graph.

Bill designs incorporate a lot of public features in order to help people figure out when bills are legit.

I do wonder how many non-visible features they hold back, in order to recognize the case when high-quality fakes have landed.

Does this actually happen, though? I mean, are there examples of hidden features on older currency?

I can't find the link now, but I remember reading an article stating there are three levels to this thing.

One, the obviously visible and known features, such that metallic strip many notes have. Know to both the users and would be counterfeiters.

The know but not obviously features, such as micro text or the things that become visible when seen under those purple lights (UV?).

Secret features only known to a very small select group of people in the money printing business. These are last resort identifiers of fakes.

What's the point when you can just counterfeit old ones?

Put simply, if you want to replace the currency in 2026, start doing it in 2016.

The existing notes are already difficult to counterfeit, though it has been achieved on occasion; this is primarily a defensive move by the Australian Reserve Bank to keep the goalposts shifting under the feet of would-be counterfeiters.

Banknotes have a limited lifespan, typically between 3 and 10 years depending on the handling characteristics of the denomination. At some point, old designs exit common circulation. At first, retailers will begin treating them with greater suspicion, then eventually stop accepting them even though they technically remain legal tender. Banks will still redeem old Australian banknotes at face value.

If a large number of new looking older bills start showing up it'll raise a lot of eyebrows so you want to get a better bill out so you can start getting the older easier to counterfeit bills out of circulation before counterfeiters figure out how to make them. It doesn't solve the problem for small transactions in whichever country since you can pass a couple older bills at a time. It does help for large cash transfers to other countries and for USD, Euro, Pound sterling, Yen, Franc, and Yuan because there's foreign reserves to think about. A large amount of US currency is held by foreign governments and banks as a foreign exchange reserve. If it was ever easy to counterfeit the latest bill a lot of the faith these foreign institutions hold in the bills legitimacy would fall apart.

Australia is pretty good at removing old notes from circulation. After a decade or so it becomes difficult to pass old notes at shops without being scrutinised very closely.

Unlike in the US, in many countries notes are not valid for all time. After an expiry date they must be exchanged at a bank for a new note.

And than they break in low temperatures? (I find only anecdotal evidence, would like to see temperature cycling like sun + clear night in a car).

Seems so old fashioned compared to crypto-currency.