These two stamps on this First-Day-Cover are coil stamps. The Japanese Ministry did not recognize coil stamps as separate issues from regular issue sheet stamps and therefore never provided an “official” first-day-cancel for any of the coil stamps. However. philatelist have always recognized coil stamps as different issues from sheets stamps.
These coil stamps were issued 1979.4.2. Kanai Stamp Co. mailed this cover with a Printed Matter advertisement to the American Philatelic Society on First-Day. Since the Ministry provided no special First Day Cancel, the stamps were cancelled with the regular postmark for International mail from Osaka, one of the three post offices where these coils stamps could be purchases over the counter.
An interesting and very unusual First-Day-Cover. A bargain at $25.
Reference: Japanese Philately Vol. 34/197-8,