FRAME STAMPS are printed individually at home or Office in to empty FRAMES bought in Japanese Post Office. Stamps are very unique , some of them are the only one in the World , Between year 2003 and 2019, 42 different frames were printed. It is very challenging to complete set. It should be on the same frame, the same nomination, similar writing, or symbols, similar subject, or colors. Very detailed information is in SAKURA catalog of Japanese Stamps, occasionally available on eBay.