These tall, thin notes (approximately 6" x 1.5", 160mm x 40mm) printed on heavy paper were known as Hansatsu.
They come in a variety of designs, ranging from simple to intricate.
Because civilians were forced to accept the Military Yen, which was not backed and could not be exchanged into Japanese Yen, it cost the Japanese government virtually nothing to purchase whatever they wanted.
The initial issues of Military currency were created by taking partially completed Japanese homeland notes and overprinting them on the front and back with four large red characters that read "Military Note". Japan issued this copper-nickel 100 Yen coin to commemorate Expo '70, held in Osaka. Seventy seven nations participated in the event and over 64 million people attended the six month event.
It is an interesting and historic gold coin that represents the end of Japan's traditional ways under the Shoguns and the introduction of new ways under the Meiji Restoration.
The note was made to be folded in half, so it could be carried like regular hansatsu.
The back is essentially blank except for seals or writing.
The 1 Mon Kanei Tsuho coin was the lowest denomination issued and served as the mainstay of the Japanese economy for over 200 years, until the Shoguns were replaced in the Meiji Restoration in 1867.
The obverse has the characters Kan Ei Tsu Ho, which translates as "Current Treasure of Kan-ei".