Yes, it's like an IOU, IOU 1 dollar, what defines how much a dollar is? What is the unit of measure? Well believe it or not, the issuer of the IOU gets to define what that is...


It's as if, in homesteading times, your neighbour had a lean year, so you lent him a bigass wooden box of potatoes, maybe a couple of hundredweight to get through the winter, and he gave you an IOU, "IOU one box of potatoes".

However, you left the box in his custody, to be returned full at some unspecified time. Now maybe he got short of firewood, maybe he got crafty, but every so often, he trimmed that box down by an inch or so, and every time you saw it, you'd scratch your head, and think "I'm sure it was bigger than that". Leanish years followed for him, or perhaps he was "forgetful", but it turned out that one year you had to tighten your belt a bit, after a mishap with your cold store, and he seemed to be doing well, so you present the IOU "One box of potatoes" and he cheerfully passes you the stunted progeny of the original crate, full to the brim with it's maximum capacity of 3 potatoes.