The Answer:

We found an answer to your question at the Web site of the Federal Reserve Bank of San Francisco.

Not only were $1 bills stamped, but $5, $10, and $20 San Francisco Reserve notes also featured the brown seal and serial numbers that the Bureau calls the "Hawaii overprint." This was done in July 1942 to keep Hawaii's paper money isolated from the rest of the U.S. in case Japan invaded Hawaii. This way the Japanese could not use the money to their advantage. It wasn't until Oct. 21, 1944 that normal monetary conditions were returned to the region.

Here's what the U.S. Dept. of the Treasury's Bureau of Engraving and Printing says about how much the bills are worth:

"The Department of the Treasury redeems all genuine United States currency at face value only, and does not render opinions concerning the numismatic value of old or rare currencies. If you wish to have your notes appraised, it is suggested that you contact a number of private collectors or dealers who are usually listed in the classified section of the telephone directory under the headings of 'Coins' and 'Hobbies.'"

This is what we suggest as well. But we do have some good news. All of the online sources we checked said that, depending on their condition, these bills are indeed worth more than their face value.

—The Editors