Thanks for the info agandau. I actually have the 20 yen note that you posted. I figured that this might be a bond of some sort because of its size (size of a piece of paper). There is a lot of writing on this note as well. It's weird that I can't find much about it because this one has a number of 041825 on it, so there must have at least 41,824 others if they started at 000001. Plus they have the 0 in front, so it is likely that a six figure number was minted of these. Still searching though.