A Japanese peso is a collectible currency which was issued in the Philippines during the Japanese occupation during World War II. It is also referred to as Japanese invasion money.
Most Japanese invasion money issued in the Philippines has very little value. The two exceptions are the 100-peso Japanese note and the co-prosperity sphere note with the message "What is it worth?" stamped on the back. The Japanese issued denominations higher than the 100 peso note, but these two are the only ones actively sought by collectors.
When the Japanese invaded the Philippines, they confiscated the local currency to purchase supplies to run their military. The currency that they replaced it with was virtually worthless.