During world War 2 the United States government made special banknotes of 1,5,10, and 20 dollar denominations with a brown seal for Hawaii and for Northern Africa they made 1 , 5 , and 10 dollars with a yellow seal so that if the enemy captured those places and started to counterfeit the money to ruin the economy they could just demonetize them. In those places they could only use the special seal currency unless they had a license to use regular cash. The values for the Hawaii notes can be anywhere from around $20 to several thousand and the north African ones can be bought for around $40 to several thousand dollars.