They are not IOU's, those have both a 'chop' and fingerprint, I have had those in the past, and the design on the paper is different. Been too many years since I have been to China, my cantonese/mandarin is too rusty to remember the characters. If they were issued by a person, they would have the 'chap' mark, haven't ever seen a Chinese Bond, but these could be something like that. I think 100 yuan is like $15.00 USD today, so I doubt they are food coupons, but the marks on them make it look like they have been cashed in. Just what little I know about Chinese debts/currencies. Strange that they are written left to right, most of the things from the bank of Hong Kong I have had has been top to bottom script.