Since all currency is just some manufactured/natural object we assign value to, from shells to gold to cash, why, in NV, is Pre-War Money not a currency? No one can really make it anymore, the mint's a glowing hole, so that solves the problem caps face (there could be a old, but functional, bottling plant for Nuka Cola raiders and nations are fighting for ad infinitum out in Vicksburg, Mississippi for all we know). It's rare, and it's canvas-plastic (I'm guessing) so it decays eventually, and it's not like a polity can't comb their local waste to obtain all caches before using it. But in 3 and NV, they're worth like 10 caps at most. In 4, it's 8 caps. 4 also basically says that a unit of pre-war money ingame is around 100 dollars pre-war, so it might be a stack of 1s. There might be a concern that due to how massive the pre-war United States was there might be literal double-digit trillions of bills out there; but we're looking at 200 years of decay on top of a nuclear war which burned most cities down. But then again, if a currency is just a mix of 'rare/hard to make/obtain thus valuable', we might end up seeing crystals or w/e used somewhere.