What's to stop people from replicating the old currency (details inside) ?

The old currency will eventually be phased out. Collectors will undoubtedly keep some but the majority will eventually be turned in at banks and replaced with the new notes. There might be some short term benefit to making bogus bills, but it will be a small window with a diminishing return on the investment.

When the banks accept the old money, they won’t recirculate it themselves. They’ll turn it in for new notes, and the old ones will be destroyed.

And when it’s only banks accepting the old cash, it means that all of the notes are subject to expert reviewers there, so it’s harder and harder to pass bogus bills.

When I used to work with Tourists travelling in my area, we would always get “old“currency
as they held onto them until they travelled to our country again.
These could have been counterfeited easily as we had no way of checking then.
In fact one time school kids duplicated the old five dollar bills using ther schools fancy new
high tech copier that easy copied the markings ( that were supposed to offset counterfeiters).
They spent hundreds of dollars in an entire week of visiting our area before anyone even noticed.
Because they were all underage one would think that they would have gotten off
easier…not so..as it is a Federal Crime.
Not sure what happened, but I do know that NO one got reimbursed for it?

Paper money doesn’t stay in circuation very long, so the old bills will become quite rare. You make a good point though. I guess as the bills begin to look unfamiliar people would scrutinize the old bills more. I so rarely use money that when I handle new bills and coins I am sometimes surprised what they look like. American coins have changed so much I think they a Canadian.

@Inspired_2write But, even the old bills were made on “money paper.” My girlfriend once was given a counterfeit bill from her bank. She didn’t realize until she had already left the bank.

At one point we were getting a lot of counterfeit bills, we too had fives passed off to us, and we were surprised, but then realized most people don’t check fives, just as you suggested.

One time I noticed a bill did not have In God We Trust on it, so I called security because the cashier had just taken in the money. We called security and they didn’t understand why it was a problem. Idiots.

The surprising thing was that the high tech photo copier even
copied the Hologram perfectly?
And how these kids fooled everyone was that they did it in groups.
That is when a cashier received one counterfeit bill, and noticed
that “if felt different”, that each casher checked it with the next
customers bill, and IF they felt the same then it wasn’t counterfeit?
Thinking was , that there was a likelyhood of counterfeit bills from
ONE customer, but NOT likely that a whole GROUP had
counterfeit bills too!
These kids executed there strategy well, and backed each other
up remarkably.
Fooled everyone, even the Banks.

Even our older Canadian money has numerous security features. Our new bills has the advantage that they will take much longer to wear out. Duplicating our older bills is still very difficult since many of the security features are known to very few people and fakes are easy to detect.