In most counties you will find letters that does not use stamps to pay the postage. A typical solution is to use postal meters machines to make labels or print direct on the letter. These meter machines are used by private firms and different authorities. The label must give the date of sending, the place name, the name of the country and the amount of postage paid. In many cases will the label also include a picture, symbol or text about the firm. These machines have to be approved by the postal administration. Postal meters have been used in international mail from 1921, but in Japan they were first used in 1950. At that time they were only used in 13 post offices sending much foreign mail. Since then a number of different machines and postal meters have been used in Japan both in private firms, authorities and the post.

My article meter stamp types at post offices is found in Japanese Philatey vol . 71 page 122-127 and vol. 72 page 177-187.