Worth clarifying on this: Self Checkout is hinged on a couple important factors: - A starting number - An open logging of all "purchases" - An ending number In that middle part, in order to ideally and openly log all purchases you would need to catalog them individually. Something like a ledger would work out well. You'd also need to make sure that everyone could read it so that they could see the progression over time, so it'd have to be an "open ledger" If you were the only one keeping track of purchases, there'd be no easy way to verify that you're telling the truth. You'd have to have a third party keep track alongside you. Ideally, you could have a bunch of third parties all keep track of things. It'd get a little weird, you'd have to have some sort of transaction cataloging, maybe with unique ids and signatures so that everyone can keep track. If you did that well, you could have a bunch of third parties validate your ledger. The bonus is that they'd all have a copy of it too, so it'd be easy to keep things open. That would make it an open, decentralized ledger. You wouldn't have to trust just 1 person, you could trust any 1, 2, 10, 100 people and they should all have the same answer. That would make it an open, trustless, decentralized ledger. If these same third parties also watch you hand the receipt to the customer at the end of the transaction, you've just done a more complex action that they can also validate! That would make it an open, trustless, decentralized execution layer. That would be the only way to do this in a transparent way, a way that would best serve the artwork. and with that, congratulations! You just created a blockchain.