Quote from: NeuroticFish on May 25, 2022, 07:07:15 AM

I find this a better path, although, yes, you have to do proper research here too.
I think that you can easily require a smartphone with NFC, it may be easier for everybody. I don't know though if only the merchant has to have the hardware, or will the customer have to have it too (in order to avoid troubles).

Satochip based hardware wallet works on NFC and its companion code is open source. Although I can guess it's not 100% what you need, you may gather some knowledge also from taking a look there. Just an idea...

A plastic trifold card could be laser-etched and sealed automatically instead of printing on paper. A mini laser engraver can be purchased for a little more than $100:

https://m.geekbuying.com/item/DAJA-DJ6-Mini-Laser-Engraver--496695.html?Currency=USD&matchtype=e&device=m&msclkid=8b00561be227195b138c349484fd34a0&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping%20US&utm_term=4575617652408320&utm_content=best%20seller&ref=w

The nfc chip can be added in a later edition.