Fungibility is a practical concept, not a legal one. Examples like crude oil, or a certain grade of steel, or yes, cash are considered fungible because there’s

Fungibility is a practical concept, not a legal one. Examples like crude oil, or a certain grade of steel, or yes, cash are considered fungible because there’s a market where buyers usually don’t care about the specific item’s history. But that’s always a simplification that breaks down in edge cases, not a 100% mathematical truth. For example, I worked on a software project where the goal was to trace a perfectly mixable material through a production chain to analyze the impact of slight contaminations that were found after the fact. The material in question would be considered fungible in most markets, but not for this specific purpose.