In 1919 the Japanese introduced “Postage Fee Paid” forms. These forms were used to pay for various kinds of mail matter in bulk. The official Japanese postal term was 郵便料金受領証原符 = Postage fee reception original form and is imprinted on top. The actual mail items received a circular bisected handstamp in characters “(post office name)/postage fee separately paid” (…/料金別納). The postage fee was pasted to the forms, which where kept by the accepting post office for a prescribed storage period.
The advantages were: for the customer one did not have to paste a postage stamp to each single mail item, and for the post office workers, they did not have to postmark each single mail item with small denomination stamps, but just paste the full amount in higher value stamps on one form.