I decided to get this if only to satisfy my curiosity.
The inscriptions translate roughly as
1988 Anata no machi no yubin kyoku – [Your local / town post office]
Fujisan me-ru pen [Mt Fuji Mail Writing]
Yubin Kitte [Post Office Stamps] Choba [accounting office] shu [collection]
The photo inscription is #30000; #36011; #28246; Lake Tanuki [an artificial lake] & Fujisan [Mt Fuji] Sakura [cherry blossom]
So this appears to be an internal / in house collection for the Japanese Post Office Stamps Accounting Office. The cover is good commercial Printing quality, similar to other Japan Booklet Panes.