[MerelyMortal]

You're correct about being able to match serial numbers, but they are still nowhere near being in the same league.

A stranger across the world can't track your physical currency in real time. Whenever serial numbers are checked (if it ever is), the tracker just knows that bill was at that spot at that time, they don't know how many times it was exchanged or where it was since it was last tracked.

With BTC, anyone can track it in real time, anywhere. The same cannot be said about physical currency.

I suppose it's not a stretch to imagine banks have a machine that scans serial numbers (eg to catch DB Cooper's cash), but I've never heard of any evidence of such machines.

[md_]

My point re: fungibility was rather that BTC's value does not come from the specific block assignment, whereas art's generally does (though I guess limited-series prints and similar might be a case where "any one of the series" has the same value).