Kicking myself firmly, now. I spent two years in Japan (1963-1965) and had easy access to a Japanese post-office, but went there only once to buy a new stamp I’d heard about. I could probably have bought every one of your souvenir sheet at face value, but I was having too much fun dating Japanese girls, buying stereos and cameras, and living the high life in Tokyo.
I did spend a fair time in Japan (2000-2005) but not the Tokyo area (like New York on Steroids). I preferred the Kyoto areas and the few stamp dealers were very accommodating. No cameras & stereos just the more profitable - kimonos and swords - no comment on the ladies
