Would the experiment require telling these friends the PIN? I suspect most people don't know 63 other humans who they could trust with their card and PIN, let alone that many humans who could be coordinated into simultaneously carrying out such a test. It's a fascinating idea though.
I think between hackerspace members and coworkers, I could easily come up with 63 trusted test partners. I'd of course do some good tracking to make sure I got all the cards back (maybe escrow one of theirs in place of mine), although that could get tricky if any ATMs got pissed off enough to start swallowing them. I guess everyone also has to record video of their attempt?
It'd be fun to coordinate, for sure. I wonder how wide a radius you'd need to cast to get 64 working ATMs....
There are a whole bunch of fun interesting questions with 64 of the "same" chip card.
With a magstripe card you can't really learn anything interesting from having more than one which you couldn't have learned with a single card and a willingness to disobey instructions from the issuer. The card is just a piece of plastic and a small amount of easily transcribed data in the magnetic stripe - so you can clone them, of course, because that's a thing crooks do, and the clones are indistinguishable.
But a chip card is more complicated, potentially much more complicated, and it will have at least some local storage that isn't transparent. This is part of why it resists cloning, you can buy gear to read and write magstripes (for legitimate purposes) very cheaply, and that's enough to clone a magstripe card, but you can't (shouldn't be able to) read enough data from your chip card to clone it.
Let's number the cards #1-64. Suppose you take card #1 and you try to buy a Coke with it from a card vending machine. Does that work? Or does it need to be "activated" by interacting with an ATM first? If it needs to be activated, after that do cards #2-10 work, or do they too need to be activated?
OK. Now having checked the first ten cards working. What happens if you go to an ATM and change your PIN on card #3 ? Does the old PIN work on card #4 still? Or does it need the new PIN even though you never told it the new PIN?
If you know somewhere that you're certain does offline PIN verification and somewhere you're sure has online (ATMs are always online) try card #5 in the offline place and card #6 in the online place, they might behave differently! In the US you may struggle to find anywhere that does offline PIN because most US outfits seem to treat card present as good enough (which is one reason why the US has very high fraud rates)
Also, find somewhere which gives out very detailed receipts with as much information as possible about your card transaction (e.g. cryptograms, and see if cards #1 and #10 are distinguishable based on the information in those receipts.
Finally, if you're aware of a transaction limit (e.g. maybe only ten contactless transactions between PIN requests) see if the limit belongs to a specific card or the account. If you know (or discover) multiple limits, there might be some in each category.
